Court Opinion

ID: 4581561
Source: CourtListenerOpinion
Date Created: 2020-10-28 21:00:21.765139+00
Date Added: 2024-06-11T08:48:01.401858
License: Public Domain

NOT PRECEDENTIAL

                         UNITED STATES COURT OF APPEALS
                              FOR THE THIRD CIRCUIT
                                 ________________

                                  Nos. 18-3795 and 18-3827
                                     ________________

                               WASHINGTON UNIVERSITY,
                                                Appellant in No. 18-3827

                                                v.

                   WISCONSIN ALUMNI RESEARCH FOUNDATION,
                                             Appellant in No. 18-3795

                                      ________________

                       On Appeal from the United States District Court
                                  for the District of Delaware
                               (D.C. Civil No. 1-13-cv-02091)
                        District Judge: Honorable Joseph F. Bataillon
                                      ________________

                       Submitted Pursuant to Third Circuit L.A.R. 34.1
                                     on April 15, 2020

                Before: CHAGARES, SCIRICA, and ROTH, Circuit Judges

                                   (Filed: October 28, 2020)
                                      ________________

                                          OPINION *
                                      ________________

*
 This disposition is not an opinion of the full Court and pursuant to I.O.P. 5.7 does not constitute
binding precedent.
SCIRICA, Circuit Judge

       Defendant Wisconsin Alumni Research Foundation (“WARF”) asks this Court to

overturn the trial court’s finding that it could not assert the statute of limitations as a

defense in a breach-of-contract dispute with Plaintiff Washington University. The trial

court determined that the statute-of-limitations defense was unavailable to WARF

because it had concealed its practice of diluting royalty payments for a patent that it

jointly owned with Washington University, withholding millions of dollars. In a bench

trial, the trial court found WARF breached the contract and awarded damages to

Washington University. But it concluded that the amount was not sufficiently certain to

justify an award of prejudgment interest. In a cross-appeal, the University asks for

prejudgment interest on the damages it received.

       We will affirm in part and reverse in part. We hold that the trial court correctly

determined that WARF could not raise the statute of limitations as a defense, but hold

that the University is entitled to prejudgment interest and will reverse and remand for

further proceedings on that issue.

                                                 I.

       In 1995, WARF and Washington University entered into the Inter-Institutional

Agreement for Prevention of Hyperphosphatemia in Kidney Disorder Patients (the

“IIA”). Among other things, the IIA, which is governed by Wisconsin law, sets the terms

for how WARF and the University would share royalties for a jointly owned and invented

                                                      2
method of treatment for chronic kidney disease. This method of treatment would

eventually receive patent protection as U.S. Patent No. 5,597,815 (“the ’815 patent”).

       Under the IIA, WARF assumed the role of the “senior party” in matters

concerning the ’815 patent, while the University was the “junior party.” As the senior

party, WARF was granted by the University the “exclusive right” to (1) “prepare, file,

prosecute, and maintain” the rights arising from the ’815 patent; (2) “negotiate, execute,

administer, and enforce” any license agreements to the ’815 patent; and (3) “determine

whether or not [WARF or the University] shall engage in and prosecute any legal

actions” involving the ’815 patent. In this role, WARF assumed the duty to keep the

junior party informed of key events and decisions relating to the parties’ jointly owned

intellectual property.

       As the junior party, Washington University retained its ownership interest in the

’815 patent but gave up its rights to commercialize, license, or enforce the patent. In

exchange for “securing and administering” any license agreements relating to the parties’

joint invention, WARF received an administration fee equaling 15% of royalties on the

’815 patent. Once these administrative fees and certain patent prosecution fees were

deducted from total revenues, WARF agreed to pay the University one-third of the

revenues from licensing the ’815 patent, with WARF keeping the remaining two-thirds.

       The IIA also set the terms for the treatment of royalties when a patent is included

in a portfolio of other patents. In the event the ’815 patent was licensed as part of a

portfolio, the parties agreed that “WARF shall have the authority to assign relative

                                                  3
values” to the ’815 patent. “Relative value” was not defined by the IIA, but the trial court

found, and neither party contests on appeal, that when the ’815 patent is included in a

portfolio of other patents, this clause requires WARF to assign to the ’815 patent “the

monetary or material worth, in light of all circumstances relevant to such license,

considered in relation to the value of the other patents licensed in the portfolio.” This is a

“patent-specific relative value.” Under the construction given to the IIA by the trial court,

“WARF cannot assign a random value to the ’815 patent,” and if some patents in a

portfolio contribute “no value to the license,” then those patents would be “assigned a

low (or zero) ‘relative value’ accordingly.”

       In 1998, WARF entered into a license agreement with Abbott Laboratories that

added the ’815 patent to a licensed portfolio of patents and patent applications. This

portfolio protected a drug, paricalcitol, that was approved by the Food and Drug

Administration to be sold commercially by Abbott under the brand name Zemplar.

Significantly, WARF recognized that the ’815 patent “directly support[ed]” Zemplar.

Zemplar would go on to be wildly successful, generating approximately $6.1 billion in

total sales revenues for Abbott. WARF would ultimately receive approximately $426.5

million in royalties from Zemplar.

       For purposes of royalty payments under the IIA, WARF assigned relative values

to the patents in the 1998 License portfolio. In its initial allocation, WARF divided 70%

of the overall value of the portfolio between two “Licensed Patents.” The remaining 30%

was divided among thirty-one “Ancillary Patents,” each of which was given an equal

                                                  4
relative value of 0.968%. The ’815 patent was included in the group of Ancillary Patents,

and WARF accordingly gave it a relative value of 0.968% of the total portfolio, the same

as the thirty other patents in the group. With the exception of the ’815 patent, all of these

patents were owned solely by WARF.

       WARF made its first distribution of Zemplar royalties to Washington University

later in 1998. Although WARF would receive approximately $426.5 million in royalties

in the coming years, it would only remit a little over $1 million to Washington

University, the co-owner of the ’815 patent. This was later found by the trial court to be

inadequate. In the trial court’s estimation, “there was no economic justification for

WARF to have assigned such a low relative value to the ’815 patent.” “Nor was there any

economic justification for WARF to have assigned the exact same relative value to each

of the other so-called ‘Ancillary Patents.’” As was eventually revealed, most of the other

Ancillary Patents had “little to no relationship to Zemplar,” with the result that WARF’s

placement of the ’815 patent in the group of Ancillary Patents was “arbitrary and self-

dealing” and served primarily to dilute the value of the ’815 patent, to the detriment of

Washington University. This remained the case even after WARF re-allocated relative

values in 1999, when WARF reduced the number of Ancillary Patents to thirty from

thirty-one and gave each patent a relative valuation of 1% of the total portfolio—all

except the ’815 patent, which continued to receive a valuation of 0.968% for the next

sixteen years.

                                                  5
       WARF’s appeal primarily revolves around the question of when Washington

University learned of this dilutionary practice. In May 1998, shortly after the launch of

Zemplar, Washington University asked WARF whether there was an “actual license

agreement” or one that “has the potential of being executed in the near future” between

WARF and Abbott, and if so, whether the University could see it. WARF confirmed the

existence of a license agreement, but represented that because of certain “confidentiality

provisions,” it was “not at liberty to provide [the University] copies of [WARF’s] license

agreements with any other parties.” Although the University did not know it at the time,

this was false—the trial court later found that the “confidentiality provisions” cited by

WARF “did not exist.” In fact, WARF was then in the process of entering into the 1998

License with Abbott, but did not share that information with the University.

       On April 4, 2001, in response to a request by Washington University, WARF

provided a few more details in a valuation letter about how it calculated the royalties it

had assigned to the ’815 patent. Though it did not identify any of the other patents in the

portfolio, WARF explained that it had assigned a value of 70% to the two Licensed

Patents in accordance with its “regular practice.” WARF also told the University that

there were thirty-one other patents in its portfolio under the 1998 License, which included

the ’815 patent. As one of the Ancillary Patents, the ’815 patent was allocated an “equal

share of the remaining thirty percent (30%) of the royalties generated by the License

Agreement,” which under the IIA entitled the University to “one third of .968 percent of

                                                 6
the total royalties generated under the [1998] license agreement” each year. WARF

further represented that “it is WARF’s policy to allocate evenly among these patents

regardless of whether or not the patent is actually currently being used by the Licensee”

because, “in many cases, it is difficult if not impossible for WARF to determine whether

or not the patent is being used by the Licensee at this time.”

       As the trial court later found, WARF’s 2001 valuation letter “was full of

misstatements, half-truths, and misdirection.” For example, several of the “policies” cited

by WARF were not actually policies at all, and though WARF averred it was “difficult if

not impossible” to determine whether a patent was currently in use, WARF had by this

time concluded, but had not told Washington University, that the ’815 patent “directly

support[ed]” Zemplar. In other words, WARF knew what Washington University did not

know—that the ’815 patent provided protection to a billion-dollar pharmaceutical.

Indeed, during this time Abbott was paying WARF 7% of earned royalties on the ʼ815

patent because of the protection it provided to Zemplar. This was not the only material

information omitted. WARF similarly knew that eight of the Ancillary Patents would

expire within the first four years of the 1998 License Agreement, but gave them the same

relative value anyway.

       Washington University did not respond to WARF’s valuation letter and did not

seek additional information until many years later. The University would not obtain a

copy of the 1998 License or have access to the calculation of relative values until

discovery in the case at bar.

                                                 7
       Litigation eventually unfolded. Starting in 2012, and unbeknownst to Washington

University, WARF and Abbott Laboratories began asserting the ’815 patent in litigation

against certain drug manufacturers. In three of these cases, the ’815 patent was the only

patent asserted to maintain Zemplar’s market exclusivity, while many of the other

Ancillary Patents had never been asserted to protect Zemplar. After receiving a third-

party subpoena from a defendant in one of these matters, Washington University learned

about WARF’s assertion of the ’815 patent in litigation and began to investigate. Soon

after, WARF and the University entered into a standstill agreement tolling the statute of

limitations for any claims relating to the IIA, effective as of April 9, 2013.

       Washington University filed this action on December 26, 2013, alleging breach of

contract and related claims. The University alleged that WARF had “breached the IIA

through its failure to assign a proper value to the ’815 Patent relative to the other

intellectual property in the [1998 License], its underpayments to Washington University

under the IIA, its failure to cooperate with Washington University with respect to

licensing of the ’815 Patent,” and through other conduct. WARF moved for summary

judgment, contending that even if it breached the IIA in 1998 by assigning a low relative

value to the ’815 patent, the University’s claims were time barred under Wisconsin’s six-

year statute of limitations for contract actions. See Wis. Stat. § 893.43. Washington

University argued WARF was equitably estopped from raising this defense because the

University had reasonably relied on WARF’s concealment of its dilution to its detriment,

                                                  8
but the trial court rejected this argument and granted summary judgment in favor of

WARF. See Wash. Univ. v. Wis. Alumni Research Found., No. CV. 13-2091 (GMS),

2016 WL 310722, at *7–10 (D. Del. Jan. 25, 2016).

       This Court reversed. See Wash. Univ. v. Wis. Alumni Research Found., 703 F.

App’x 106 (3d Cir. 2017). On the issue of equitable estoppel, we found “there [was]

clearly a genuine dispute of fact regarding whether Washington University knew that

WARF’s statements regarding confidentiality and assignment of value were inaccurate,”

and concluded that the trial court erred when it held that equitable estoppel was

inapplicable as a matter of law. Id. at 110. We also remanded for further proceedings on

the applicability of Wisconsin’s “continuing violation” exception to the statute of

limitations. Id. at 109; see, e.g., Noonan v. Nw. Mut. Life Ins. Co., 687 N.W.2d 254, 262

(Wis. Ct. App. 2004).

       After holding a bench trial on remand, the trial court found WARF liable for

breach of contract because, among other things, WARF had failed to provide a “patent-

specific relative value” of the ’815 patent, which was “one of the most important patents

in the 1998 Abbott License.” Instead of the 0.968% relative value given by WARF, the

trial court found, relying on expert testimony, that the ’815 patent should have received a

much higher relative value of 27.1%. The trial court also found that WARF was equitably

estopped from asserting a statute of limitations defense, finding “clear and convincing”

evidence that WARF had concealed the information that Washington University needed

for determining it had a claim and that the University had reasonably relied on WARF’s

                                                9
representations to its detriment. In the alternative, the trial court also found that because

the IIA imposed an annual “duty to revalue” the ’815 patent, the “continuing violation”

exception to Wisconsin’s statute of limitations applied.

       The trial court then calculated the damages to be awarded to Washington

University. Because the assigned relative value was so low—0.968% of the total

portfolio’s value instead of 27.1%—the trial court awarded $31,617,498 in compensatory

damages to the University. But the trial court denied prejudgment interest on this sum.

The court recognized that the University’s damages were determinable “by reference to

some objective standard,” as they must be for prejudgment interest to be awardable under

the applicable Wisconsin law. Even so, since there was a “reasonable range of patent-

specific relative values between 27.1% and 33%,” the trial court held that “it cannot be

said that this reasonable standard of measurement or the correct application of which one

was sufficiently certain to ascertain the amount owed before this lengthy opinion.”

                                                II. 1

       Two sets of issues are before us. WARF argues that Wisconsin’s six-year statute

of limitations barred Washington University from bringing suit in December 2013. See

Wis. Stat. § 893.43. As a preliminary matter we note two points of agreement. First,

neither party disputes that Washington University filed well past this deadline. See CLL

1
    The District Court had jurisdiction pursuant to 28 U.S.C. § 1332(a)(1), and we have
    jurisdiction pursuant to 28 U.S.C. § 1291.
                                                   10
Assocs. Ltd. P’ship v. Arrowhead Pac. Corp., 497 N.W.2d 115, 117 (Wis. 1993) (“[I]n an

action for breach of contract, the cause of action accrues and the statute of limitations

begins to run from the moment the breach occurs. This is true whether or not the facts of

the breach are known by the party having the right to the action.” (citations omitted)).

Second, neither party contests that WARF breached the IIA by assigning a low relative

value to the ’815 patent. Therefore, WARF’s challenges are limited to whether the trial

court (1) correctly determined that WARF is equitably estopped from asserting the statute

of limitations through its conduct or, in the alternative, (2) properly construed the IIA

and, in consequence, correctly applied Wisconsin’s “continuing violation” exception to

the statute of limitations.

       In its cross-appeal, Washington University seeks review of the trial court’s

conclusion that WARF did not have to pay prejudgment interest on $31,617,498 in

compensatory damages because, in the trial court’s view, there was not a “reasonable

standard of measurement” that would make damages “sufficiently certain to ascertain the

amount owed” until the court issued its “lengthy opinion.”

       Our analysis begins with WARF’s challenge to the trial court’s equitable estoppel

findings. Equitable estoppel is a legal question with underlying factual questions. See

May v. May, 813 N.W.2d 179, 183–84 (Wis. 2012) (“The determination of whether

equitable estoppel may be applied to an uncontested set of facts is a question of law that

we review independently of the previous court decision.”). We review a district court’s

                                                 11
findings of fact for clear error and its conclusions of law de novo. See VICI Racing, LLC

v. T-Mobile USA, Inc., 763 F.3d 273, 282–83 (3d Cir. 2014).

        Equitable estoppel prevents a defendant from asserting the statute of limitations

when it “has engaged in fraudulent or wrongful conduct, and the other side has relied on

the conduct to its detriment.” Policemen’s Annuity & Ben. Fund, Milwaukee v.

Milwaukee, 630 N.W.2d 236, 243–44 (Wis. Ct. App. 2001). The doctrine applies when

there is “(1) action or non-action; (2) on the part of one against whom estoppel is

asserted; (3) which induces reasonable reliance thereon by the other, either in action or

non-action; (4) which is to the relying party’s detriment.” Wash. Univ., 703 F. App’x at

109 (quoting Affordable Erecting, Inc. v. Neosho Trompler, Inc., 715 N.W.2d 620, 628

(Wis. 2006)). We have already held that the doctrine is applicable in these circumstances

as a matter of law, and directed the trial court to resolve four genuine issues of material

fact:

        (1) whether WARF concealed information Washington University
            needed to determine if it had a valid claim;
        (2) whether that information was necessary to pursue the claim;
        (3) whether Washington University reasonably relied on WARF’s
            statements and conduct; and
        (4) whether Washington University had the ability to obtain that
            information, notwithstanding WARF’s alleged concealment.

Id. at 110.

        On remand, the trial court resolved each question in favor of the University. It

found there was “extensive” evidence that WARF had “actively concealed, and refused to

share, the very information that WashU needed to determine that it had a valid claim for

                                                 12
breach of contract” arising from the relative value given to the ’815 patent. It

consequently held that WARF was equitably estopped from asserting a statute-of-

limitations defense.

       We find no clear error. Despite its obligation to act in the parties’ mutual benefit

as the “senior party” under the IIA, WARF invoked “confidentiality provisions” that

simply “did not exist,” concealed critical information about the ’815 patent, obscured the

nature of the patents in the 1998 License portfolio, and did not disclose WARF’s internal

valuation methodologies. Perhaps most pertinently, the trial court found that “WARF

assigned equal value to numerous patents that had nothing to do with paricalcitol and hid

this from WashU for as long as possible,” a practice that “systematically diluted the

relative value of the ’815 patent.”

       WARF does not seriously challenge any of these factual findings. Instead, it

presents a series of arguments to the effect that Washington University should have

known about WARF’s dilution of royalties for the ’815 patent in spite of WARF’s

actions. None is persuasive. Although WARF contends that “all the information WashU

ever would have needed [about breach of the IIA] was supplied within the ‘four corners’

of the IIA and available to WashU all along,” this is not enough for the University to

know of WARF’s breach. Knowledge that a party has agreed to perform is not the same

as knowledge of actual performance, and the University had no access to the details of

WARF’s performance until it learned about the value of the other patents in the portfolio

years later.

                                                 13
       We also reject WARF’s contention that the University should have known about

its dilutionary practices when it told the University in its 2001 valuation letter that it had

given each of the Ancillary Patents, including the ’815 patent, an “equal share” of the

portfolio’s value. WARF did not breach the IIA simply by giving an “equal share” to the

’815 patent; it breached the IIA by “systematically dilut[ing]” the ’815 patent through a

convoluted scheme and then hid that scheme from Washington University “for as long as

possible.” The issue here is not that the ’815 patent received a mathematically “equal”

value, but that it received an inadequate value far beneath its “relative” value.

       In its final factual challenge, WARF argues that it told the University about its

valuation practices in its 2001 valuation letter. Yet the trial court determined that this

letter was false and deceptive because it “created the false impression that WARF was

unable to determine whether any of the Ancillary Patents, including the ’815 patent,

supported the development and commercialization of paricalcitol/Zemplar.” By this time,

WARF had already determined, but had not told the University, that the ’815 patent

“directly support[ed] Zemplar,” and also knew that eight of the patents in the ancillary

portfolio were slated to soon expire but gave them the same valuation anyway. We hold

that the record amply supports the trial court’s findings.

       We turn now to WARF’s legal challenges to the trial court’s equitable estoppel

holding. In its first argument, WARF contends that the trial court applied the wrong legal

standard for equitable estoppel because it failed to consider whether WARF’s conduct

                                                  14
caused the University to file suit many years after WARF’s breach in 1998. 2 Distilled to

its essence, WARF’s argument is that even though the trial court found that Washington

University “relied” on WARF’s conduct and misstatements, those conduct and

misstatements did not “cause” the University to file until after the statute of limitations

had lapsed. Because the trial court did not break out causation from the reliance inquiry,

WARF argues, its holding was error.

       We fail to see the distinction, at least in these circumstances. If the University’s

“reliance” on WARF’s statements and conduct did not cause it to fail to file within the

statutory period, then it can hardly be said to have relied on those statements and conduct

to its detriment. Causation is implicit in the element of “reliance”; the terms are often

used interchangeably under Wisconsin law, as well as the law of other jurisdictions. See,

e.g., Ramsden v. Farm Credit Servs. of N. Cent. Wisconsin ACA, 590 N.W.2d 1, 8 (Wis.

Ct. App. 1998) (“Reliance, in a negligent misrepresentation claim, is equivalent to the

causation element . . . .”); see also Erica P. John Fund, Inc. v. Halliburton Co., 563 U.S.

804, 812 (2011) (noting that within the context of a Rule 10b-5 action for securities

fraud, “the element of reliance” is often referred to as “transaction causation”); Astor

Chauffeured Limousine Co. v. Runnfeldt Inv. Corp., 910 F.2d 1540, 1546 (7th Cir. 1990)

2
    To the extent that WARF challenges the trial court’s factual findings on reliance through this
    line of argument, there was substantial evidence to support the trial court’s findings. The trial
    court found that “[a]bsent critical information from the 1998 License, namely that the ’815
    patent was exclusively licensed . . . and that the ’815 patent was included in a group of
    ‘Ancillary Patents,’ . . . WashU lacked the ability to determine for itself whether it had a
    valid claim against WARF for breach of contract.”
                                                     15
(“[R]eliance means only the conjunction of materiality and causation . . . .”). Tellingly,

WARF’s arguments at the trial court reveal the same reality: to the extent that WARF

even argued that causation was a separate element, that argument was indistinguishable

from WARF’s arguments about detrimental reliance.

       So the fact that the trial court did not make a separate finding on causation is

unremarkable here. When the trial court concluded that “WashU reasonably relied on

WARF’s statements and conduct,” that conclusion could only be read to contemplate a

material degree of causation. That the trial court did not explicitly say as much is beside

the point. A court’s findings are adequate if “they are sufficiently comprehensive and

pertinent to the issues to provide a basis for decision.” Zimmerman v. Montour R.R. Co.,

296 F.2d 97, 98 (3d Cir. 1961); see also VICI Racing, 763 F.3d at 297–98 (“A trial

court’s findings are sufficient if the affirmative facts found by it, construed as a whole,

negate a rejected contention.”); State v. Fishnick, 378 N.W.2d 272, 281 (Wis. 1985)

(“[T]his court will not reverse a trial court’s ruling if the ruling is correct and the record

reveals a factual underpinning that would support the proper findings.”). We accordingly

reject WARF’s argument that the trial court applied the wrong standard. 3

       In its second legal challenge to the trial court’s equitable estoppel holding, WARF

argues that the trial court wrongly imposed a duty on WARF to tell Washington

3
    As for WARF’s contention that equitable estoppel requires not just a finding of causation but
    rather a finding of but for causation, we will not address that question because WARF did not
    raise it below. See Freeman v. Pittsburgh Glass Works, LLC, 709 F.3d 240, 249 (3d Cir.
    2013) (“We generally refuse to consider issues that the parties have not raised below.”).
                                                   16
University about its breach. As WARF notes, a defendant may be subject to equitable

estoppel if it “took active steps to prevent the plaintiff from suing,” such as by

“concealing evidence . . . that [the plaintiff] needed in order to determine that he had a

claim.” Barry Aviation Inc. v. Land O’Lakes Mun. Airport Comm’n, 377 F.3d 682, 689

(7th Cir. 2004) (cleaned up). Applying the inverse of this proposition, WARF contends

that because, in its view, the trial court found that it did not take “active steps” to deceive

the University, it cannot be equitably estopped from asserting a statute-of-limitations

defense.

       But this argument fails too. First, the trial court actually did find that WARF

“actively concealed, and refused to share” necessary information. But even without that

finding, WARF had a duty under the IIA “to communicate, in a timely manner, all

material information concerning the [’815 patent] that is available to WARF and that is

relevant to the licensing thereof.” Therefore we reject this contention as well, and will

affirm the trial court’s holding on equitable estoppel. Because we affirm on these

grounds, we need not consider the trial court’s alternative holding on the applicability of

the “continuing violation” exception to Wisconsin’s statute of limitations.

       We now consider Washington University’s cross-appeal for prejudgment interest.

The University asks this Court to increase its judgment by 5% in prejudgment interest

through the entry of judgment on November 26, 2018. See Wis. Stat. § 138.04.

                                                  17
Entitlement to prejudgment interest is a question of law that we review de novo. See

Beacon Bowl, Inc. v. Wis. Elec. Power Co., 501 N.W.2d 788, 802 (Wis. 1993).

       Under Wisconsin law, “he who retains money which he ought to pay to another

should be charged interest upon it.” Laycock v. Parker, 79 N.W. 327, 335 (Wis. 1899).

Courts may award prejudgment interest to compensate a plaintiff for “the value of the use

of the money—a value which should be accruing for the benefit of the plaintiff-creditor”

but “was accruing to the defendant-debtor instead.” Johnson v. Pearson Agri-Sys., Inc.,

350 N.W.2d 127, 131 (Wis. 1984). Prejudgment interest may be awarded if “there is a

reasonably certain standard of measurement by the correct application of which one can

ascertain the amount he or she owes,” Teff v. Unity Health Plans Ins. Corp., 666 N.W.2d

38, 53 (Wis. Ct. App. 2003), and damages are ascertainable when a defendant “could

have determined at least the upper limit of its liability with reasonable certainty.” Fattore

Co. v. Metropolitan Sewerage Comm’n of Milwaukee Cty., 505 F.2d 1, 7 (7th Cir. 1974)

(applying Wisconsin law); see also 24 Williston on Contracts § 64:12 (4th ed. 2019)

(noting that damages may be ascertained “if a reasonable basis for computation of

damages is afforded, even though the result will only be approximate”).

       Although the trial court admirably handled the complex web of issues before it, we

believe it erred by denying prejudgment interest to Washington University. If WARF

does not have to pay prejudgment interest here, then it would be the beneficiary of a

$31,617,498 interest-free loan, denying the University the time value of its wrongfully

withheld royalty payments. Cf. Johnson, 350 N.W.2d at 131. Nothing in Wisconsin law

                                                 18
supports such an entitlement. Far from finding this valuation incalculable, WARF itself

assigned a relative value to the ’815 patent of 0.968% which—though leagues away from

the 27.1% later determined to be accurate by the trial court—indicates that WARF was

capable, in theory if not in practice, of applying some objective measurement to the

relative value of the ’815 patent.

       The parties’ now-longstanding dispute about liability in this matter does not alter

the outcome here. Even if the ’815 patent was “grossly undervalued” and became the

subject of contentious debate, that disagreement does not furnish a basis to deny

prejudgment interest. “Mere difference of opinion as to amount is . . . no more a reason to

excuse [a party] from interest than difference of opinion whether he legally ought to pay

at all, which has never been held [to be] an excuse.” Giffen v. Tigerton Lumber Co., 132

N.W.2d 572, 575 (Wis. 1965) (quoting Laycock, 79 N.W. at 335). Although the trial

court heard varying testimony on a range of relative values that should have been

allocated to the ’815 patent, we do not find this range to be uncertain enough to deny the

award of prejudgment interest. “Where the amount owed is readily ascertainable and not

paid, the withholding party should be held responsible for making such determination

correctly and liable for interest.” Klug & Smith Co. v. Sommer, 265 N.W.2d 269, 272

(Wis. 1978). As such, we find that Washington University is entitled to prejudgment

interest. We will accordingly vacate the trial court’s order on that limited issue and

remand for further proceedings consistent with this opinion.

                                                19
                                              III.

       For the reasons set forth above, we will affirm in part and reverse in part the

judgment of the trial court.

                                                20