In the
 United States Court of Appeals
               For the Seventh Circuit
                         ____________

No. 04-1905
EMPLOYERS INSURANCE OF WAUSAU,
                                                 Plaintiff-Appellee,
                                v.

TITAN INTERNATIONAL, INC. and
  DYNEER CORPORATION,
                                           Defendants-Appellants.
                         ____________
            Appeal from the United States District Court
                for the Central District of Illinois.
              No. 02 C 3060—Jeanne E. Scott, Judge.
                         ____________
     ARGUED DECEMBER 8, 2004—DECIDED MARCH 3, 2005
                         ____________



  Before FLAUM, Chief Judge, and POSNER and SYKES,
Circuit Judges.
  POSNER, Circuit Judge. The appeal in this diversity suit
presents issues of appellate jurisdiction and Illinois contract
law in the setting of a dispute over insurance coverage.
Wausau had issued a number of workers’ compensation,
auto liability, and general liability policies covering the
defendants. The policies contained provisions for adjusting
the premiums retrospectively (“retros”) if the loss experi-
ence differed substantially from what the parties
2                                                   No. 04-1905

had expected when the policies were negotiated; such
provisions are common, e.g., Casualty Ins. Co. v. Hill Mechan-
ical Group, 

, 372 (Ill. App. 2001); Pre-Fab
Transit Co. v. Northbrook Property & Casualty Ins. Co., 

, 869 (Ill. App. 1992); Edward Gray Corp. v.
National Union Fire Ins. Co., 

, 367-68 (7th Cir.
1996); Liberty Mutual Ins. Co. v. Nippon Sanso K.K., 

, 157 (1st Cir. 2003), in situations in which risk is difficult
to determine in advance. 5 Lee R. Russ & Thomas F. Segalla,
Couch on Insurance § 69.15 (3d ed. 1996). The price of an
insurance policy is a function of the risk that the loss
insured against will occur; if that risk cannot be calculated,
the price will be arbitrary; hence the need for a retroactive
adjustment.
   Because of a computer error in calculating the retro
adjustment for 2000, Wausau overlooked losses that it
had incurred under the policies and as a result mistak-
enly sent the defendants a check for $239,132; when it
discovered the mistake it demanded the return of the money
plus $3,987 in retrospectively adjusted premiums due from
the defendants. They refused both demands, and Wausau
brought this suit for the sum of the two amounts, $243,119.
We’ll call this the “base amount.” On November 14, 2003,
the district court granted summary judgment for Wausau
and entered a judgment for the base amount. Both sides
filed timely Rule 59(e) motions to amend the judgment. The
defendants wanted the judgment for Wausau thrown out.
The plaintiffs wanted prejudgment interest added to the
base amount. They also wanted an award of costs, and they
demanded it in the same motion, but they correctly cited
Fed. R. Civ. P. 54(d)(1) as the basis for the demand. Unlike
an award of prejudgment interest, an award of costs does
not alter or amend the judgment and so is not within the
scope of Rule 59(e). Buchanon v. Stanships, Inc., 

,
No. 04-1905                                                  3

268-69 (1988) (per curiam); United States v. Deutsch, 

, 301 n. 2 (7th Cir. 1992); Lorenzen v. Employees Retirement
Plan of Sperry & Hutchinson Co., 

, 231 (7th Cir.
1990).
  On February 4, 2004, the district court issued an order
denying the defendants’ motion for reconsideration but
granting Wausau both the prejudgment interest and the
costs that it had sought. The defendants did not appeal
within 30 days of that order. On March 11, the district
court issued a judgment order captioned “Amended
Judgment in a Civil Case” and described in the body of the
order as a judgment entered pursuant to Fed. R. Civ. P. 58.
The judgment was for the base amount, the prejudgment
interest, and the costs, all in the amounts specified in the
February 4 order. The defendants appealed within 30 days
of the March 11 judgment. Wausau argues that that was too
late.
  Rule 58 requires that “every judgment and amended
judgment must be set forth on a separate document”
(separate from the ruling or opinion pursuant to which
the judgment is being entered) except, so far as bears on this
case, “an order disposing of a motion . . . to alter or amend
the judgment, under Rule 59.” Fed. R. Civ. P. 58(a)(1)(D). If,
as in the case of such an order, no separate document is
required, the time of entry of judgment (hence the time
when the period within which to appeal begins to run) is
when the order is entered on the court’s docket, while if a
separate document is required, the time of entry of judg-
ment is when that document is docketed. Fed. R. Civ. P.
58(b). (If, though required, a separate document is for some
reason not issued, the time of entry of judgment is 150 days
after the judgment was docketed. Fed. R. Civ. P. 58(b)(2)(B).)
Wausau argues correctly that insofar as its postjudgment
4                                                 No. 04-1905

motion sought merely an award of costs, the filing of the
motion did not toll the time for the defendants to appeal
from the original judgment, Fed. R. App. P. 4(a)(1)(A),
(4)(A); Buchanon v. Stanships, 

, 485 U.S. at 268-69;
Lorenzen v. Employees Retirement Plan of Sperry & Hutchinson

, 896 F.2d at 231; Moody National Bank v. GE Life &
Annuity Assurance Co., 

, 250 (5th Cir. 2004), the
one that had been entered on November 14, 2003. What did
toll the time for appeal, says Wausau, were the two Rule
59(e) motions. But they were disposed of on February 4.
Wausau concludes that since an order disposing of a Rule 59
motion is not required to be set forth on a separate docu-
ment, the 30 days within which the defendants had to file a
notice of appeal started to run on February 4.
  But the district judge entered an amended judgment on
March 11; and Rule 58 requires, as we know, that every
amended judgment be set forth on a separate docu-
ment—and when a separate document is required, the
time to appeal runs from the date on which that docu-
ment was docketed, provided it is docketed within 150 days
after the judgment, a condition satisfied here.
  The only way to reconcile the requirement that an
amended judgment be set forth in a separate document with
the exception to that requirement for an order disposing of
a Rule 59(e) motion is by reading “disposing of a motion” as
“denying a motion.” The reading is supported, though
muddily, by the Committee Note to the 2002 Amendment
to Rule 58. The note states that “if disposition of the [Rule
59(e)] motion results in an amended judgment”—as it did
here—“the amended judgment must be set forth on a
separate document,” as it was, on March 11. Granting a
motion is one way of “disposing” of it, but when a motion
to amend a judgment is granted, the result is an amended
No. 04-1905                                                   5

judgment, so the rule becomes incoherent if “disposing” is
read literally, for then the order granting the motion both is,
and is not, an order required to be set forth in a separate
document. Nonsensical, or as here logically impossible,
interpretations of statutes, rules, and contracts are unaccept-
able. Clinton v. City of New York, 

, 428-29 and n.
14 (1998); United States v. X-Citement Video, Inc., 

,
68-70 (1994); Treadway v. Gateway Chevrolet Oldsmobile
Inc., 

, 976 (7th Cir. 2004); FutureSource LLC
v. Reuters Ltd., 

, 284-85 (7th Cir. 2002); Hughey v.
JMS Development Corp., 

, 1529-30 (11th Cir.
1996). So we are driven to interpret “disposing” as “deny-
ing,” not “granting or denying,” and thus we conclude that
the defendants’ appeal was timely, because it was an appeal
from an amended judgment and thus from a grant rather
than a denial of a Rule 59(e) motion. And so we proceed at
last to the merits.
   The defendants do not doubt that Wausau made a
computational error but for which it would have charged
them the additional $3,987 in premiums rather than sending
them the huge refund check. But they say that Wausau
failed to prove that the “correct” amount was actually
compliant with the insurance policies. Each state specifies
the method that the insurer must use to compute rates, e.g.,
N.Y. Ins. Law § 2304(a); 215 ILCS 5/456-5/458, 5/462b; Ind.
Code §§ 27-1-22-3 through -5, including retros, Sandwich
Chef of Texas, Inc. v. Reliance National Indemnity Ins. Co., 

, 211-13 (5th Cir. 2003), and the defendants insist
that Wausau’s burden of proving that their refusal to honor
its retro demands required Wausau to prove that it used the
correct “state factors” (as the methods specified by states for
computing rates are called) in calculating the amount
that the defendants owed it.
6                                                No. 04-1905

   The argument misunderstands the burden of proof in a
contract case. If the seller presents a bill to the buyer, the
buyer refuses to pay, and the seller sues, the seller’s
initial burden of production merely requires that it sub-
mit the contract and show how the amount that it is seeking
is derived from the contract’s terms. See, e.g., Alco Standard
Corp. v. F & B Mfg. Co., 

, 509 (Ill. App. 1970),
reversed on other grounds, 

(1972); Long v.
Reeves Southeastern Corp., 

(Ga. App. 2003);
Collins v. Guinn, 

, 836 (Tex. App. 2003);
Campbell, Maack & Sessions v. Debry, 

, 991 (Utah
App. 2001). Wausau did that. It showed how the terms of
the policies, in light of the losses that it had experienced
under the policies, required the retrospective premium
adjustment that it sought, so that the defendants’ refusal to
comply was a breach. The listed terms included each state
numerical factor used to compute the retrospective pre-
mium adjustments. If the defendants thought that the
numerical factors were incorrect—were not what state law
prescribed—it was their burden to present evidence of this
fact, as they could easily have done, since the factors are
derived from public acts of the state agencies that regulate
insurance. The defendants did not do this, insisting instead
that the burden of proof was on Wausau. That amounts to
the frivolous argument that to prove a breach of contract the
plaintiff cannot rely on what the contract says but must
prove that every term corresponds to some true fact in the
world. So if the contract is dated March 11, 2004, the
plaintiff must present evidence that, yes, indeed, that is
when the contract was signed. The enforcement of contracts
would be paralyzed by any such requirement.
  Although it should thus have been easy for the defendants
to obtain the information they needed in order to verify the
No. 04-1905                                                    7

accuracy of Wausau’s computations, our decision would not
be altered if, as they claim, they needed discovery from
Wausau to obtain it and Wausau dragged its feet. The
defendants never sought a court order compelling the
production of the information, and such an order is a
prerequisite to imposing a sanction for discovery abuse.
Fed. R. Civ. P. 37(b)(2); Halas v. Consumer Services, Inc., 

, 164 (7th Cir. 1994); In re Williams, 

, 89 n.
1 (1st Cir. 1998); Shepherd v. American Broadcasting Cos., 

, 1474 (D.C. Cir. 1995). And before such an order
can be entered the movant must certify that he “in good
faith conferred or attempted to confer” with his recalcitrant
opponent. Fed. R. Civ. P. 37(a)(2)(A), (d); Naviant Marketing
Solutions, Inc. v. Larry Tucker, Inc., 

, 186-87 (3d
Cir. 2003). The defendants didn’t do that either.
   The issue of burden of proof is fogged somewhat by
Wausau’s insistence that illegality is an affirmative de-
fense to the enforcement of a contract and of course defen-
dants have the burden of proving affirmative defenses. That
is true but irrelevant. The issue here is not illegality. No one
supposes that any of the insurance policies in issue in this
case violates the law or public policy of any state and is
therefore unenforceable. The issue is the meaning of the
contracts, which depends in part on the state factors because
they are incorporated in the contracts by operation of law.
If Wausau used the wrong state factors, then it is not
contractually entitled to the retrospective premiums it is
seeking; that is all.
  Wausau has an alternative theory of entitlement to the
return of the $239,132 that it sent the defendants in error:
restitution for money paid by mistake. Illinois Graphics Co. v.
Nickum, 

, 1293 (Ill. 1994); Allstate Life Ins. Co.
v. Yurgil, 

, 285 (Ill. App. 1994); Bank of
8                                                 No. 04-1905

Naperville v. Catalano, 

, 444 (Ill. App. 1980).
The defendants argue that it was a careless mistake
and therefore restitution should be denied. There is no
“therefore.” Probably the mistake was careless; but the
law does not permit a person to keep money that he
has received by mistake, just because the mistake is careless.
St. Paul Federal Savings & Loan Ass’n v. Avant, 

, 1057 (Ill. App. 1985); Bank of Naperville v. 

, 408 N.E.2d at 445; Century Building Partnership, L.P. v.
SerVaas, 

, 974 (Ind. App. 1998). Such a rule
would make people too careful, penalizing them for mis-
takes that caused nobody any harm and so should not be
penalized at all—the defendants do not argue that having to
return their windfall will cause them harm beyond the
natural disappointment that one is bound to feel at having
to cough up money to someone else, for whatever reason.
The law is not finders keepers, unless the property found
has been abandoned, which is to say deliberately relin-
quished, not merely lost or misplaced. Hendle v. Stevens, 

, 833 (Ill. App. 1992); Kahr v. Markland, 

, 582 (Ill. App. 1989); Michael v. First Chicago Corp., 

, 408-09 (Ill. App. 1985). It would be absurd to
suppose that if Wausau owed the defendants $1 and by the
careless mistake of one of its clerks issued them a check for
$1 million, they could keep the $1 million because the
mistake was a careless one. But that is their argument.
  Finally, since the suit was for a precisely calculable
amount of money, the district court was acting in confor-
mity with Illinois law in awarding the plaintiff prejudgment
interest. 815 ILCS 205/2; Lyon Metal Products, L.L.C. v.
Protection Mutual Ins. Co., 

, 510 (Ill. App.
2001); Ervin v. Sears, Roebuck & Co., 

, 250
No. 04-1905                                                 9

(Ill. App. 1984); Zayre Corp. v. S.M. & R. Co., 

,
1157 (7th Cir. 1989) (Illinois law).
                                                  AFFIRMED.

A true Copy:
        Teste:

                          _____________________________
                           Clerk of the United States Court of
                             Appeals for the Seventh Circuit




                    USCA-02-C-0072—3-3-05