ON MOTION FOR REHEARING Defendants urge on rehearing that we erroneously considered the agreement to be an executory accord, citing as authority RESTATEMENT OF CONTRACTS Â§ 419 (1932) which creates a presumption of a satisfaction through the execution of a substitute agreement when the underlying claim is unliquidated. The damages sought here by plaintiffs' underlying claim are capable of a definite ascertainment. The action is one for breach of express trust and the imposition of constructive trusts on property and upon production payments. These are not matters to be arrived at by conjecture, like pain and suffering in a personal injury case. They are subject to a precise calculation. Accordingly, the presumption noted in Â§ 419 of the RESTATEMENT OF CONTRACTS has no application. Our holding is based upon an examination of the face of the agreement which does not reveal that it was entered into in accord and satisfaction in the light of defendants' burden to establish the defense of accord and satisfaction. See Jenkins v. Henry C. Beck, 449 S.W.2d 454 (Tex.1969). Upon retrial, the surrounding facts and circumstances may create a fact issue as to whether the parties intended the agreement to operate in satisfaction of the underlying claim or merely to hold it in abeyance until performance. Compare Ferguson-McKinney Dry Goods Co. v. Garrett, 252 S.W. 738 (Tex.Com.App.1923, holding approved) with Scott v. Ingle Bros. Pacific, Inc., 489 S.W.2d 554 (Tex.1972) and Murphy v. Dilworth, 137 Tex. 32, 151 S.W.2d 1004 (1941). We note that this may be one of several fact issues that may be raised by the pleadings and the evidence, including agreement, repudiation and fraud. We needed only to find one such fact issue, repudiation, that the court below erroneously decided without benefit of trial by jury.