1196 CROSS REFERENCE Consideration illegal in part, see sections 523 and 524. SEC . 529. CONSIDERATION EXECuisD OR w ~tRCUTORY:A co nside ra- tion' may be executed or executory, in whole or in part . In so far as it is executooy it is subject to the provisions of sections 520 to 524 . SEC. 530. EXE CUTORY coNSmmwrroN .- Wh en a consideration is executory. it is not indispensable that the contract should specify its amount or the means of ascertaining it . It may be left to the decision of a third person, or regulated by any specified standard . SEC. 531 . HOW ASCERTAINED .-When a contract does not determine the amount of the consideration, nor the method by which it is to be ascertained, or when it leaves the amount thereof to the discretion of an inter ested party , the consi derat ion mu st be so much money as the object of the contract is reasonably worth . EBeet of im ossihff - - SEC. 532. Errr CT OF IMPO SSIBIL ITY OF ASCERTA INING CONSIDE RA- of assert
g con si ity deration .
TION-Where a contract provides an exclusive method by which its consideration is to be ascertained, which met hod is on its face impos- sible of execution, the entire contract is void . SEC . 533. SAME .-Where a contract provides an exclusive method by which its consideration is to be ascertained, which method appears possible on its face, but in fact is, or becomes, impossible of execution, such provision only is void . CROSS R FswoE Effect of partial invalidity of contract, see section 524. SEC . 534 . WRITTEN INSTRUMENT PRESUMPTIVE EVIDENCE OP CONem- F.RATION .-A written instrument is presumptive evidence of a con- sider ation . Ante, p.1195. "•onsideration exe- cuted or executory . Execntory. How ascertained . Amte, p . 1195. Written instrument presumptive evidence of consideration . Post, p. 1197 . Post, p. 1311 . Burden of proof t~ invalidate . MANNER OF CRE ATIN G CON- TRACTS. Contract, express or implied . Express contract . Implied contract . Pos t, p. 1203. Oral contracts . Post, p .1204. Contr acts not in writ- ing, throu gh fr aud . 72d CONGRESS . SESS. I L CH. 128. FEBRUARY 27, 1933 . .CROSS R .ErEanIWES Distinction between sealed and unsealed instruments abolished, see section 545. Presumption of consideration for negotiable instrument, see section 1423 . SEC . 535 . BURDEN OF PROOF TO INVALIDATE sur'e1CIENT CONSIDERA- TION .-The burden of showing a want of consideration sufficient to support an instrument lies with the party seeking to invalidate or avoid it . CHAPTER 29 .-MANNER OF CREATING CONTRACTS SEC. 536. CO NTR ACT S, EXP RES S OF IMPLI ED .- A contract is either express or implied . SEC . 53 7. EXPRESS CONTRACTS, w$AT.- A n express contract is one the terms of which are stated in words . SEC . 538. IMPLIED CONTRACT , WHAT . -An im pli ed con tr act is one the existence and terms of which are manifested by conduct. CR OSS REFERENCE Obligations imposed by law, see sections 589 et seq . SEC. 539 . WHAT CONTRACTS MAY BE ORAL .-All cont racts may be oral, except such as are specially required by statute to be in writing, CROSS REFrut rccE Contracts when to be in writing, see sections 540, 541, and 800. SEC . 540 . CONTRACT NOT IN WRITING THROUGH FRAUD, MAY BE ENFORCED AGAINST FRAUDULENT PARTY.-Where a contract, which is
