Tiffany offers to sell her diamond brooch to Melba, for a certain price if she accepts before 10 a.m. Monday, after which she will put it up for auction. Tiffany may revoke the offer

a. after 10 a.m. Monday.

b. only after midnight Monday.

c. within twenty-four hours before 10 a.m. Monday.

d. within a reasonable time before 10 a.m. Monday.

17. On Monday, Fredo tells Sonny that he will pay Sonny $500 if a variety of tasks are completed by Friday. On Wednesday, when Sonny is more than half done with the work, Fredo says that he meant to also get Sonny to do some other things as part of the original contract, which he now wants Sonny to do, but refuses to pay Sonny any more than the original $500 offer. Fredo and Sonny had

a. an expired contract when Fredo said that he had changed his mind.

b. a bilateral contract when Fredo said that he would pay for certain work.

c. a unilateral contract as soon as Sonny began to perform the originally agreed- upon tasks.

d. no contract

18. Under a contract with McDonald's Farms, EIEIO Construction begins digging an agricultural pond. In mid-project, EIEIO demands $40,000 over the contract price, claiming that it appears to be a little more complicated than EIEIO had first estimated, but not elaborating as to what precisely is more complicated. McDonald's thinks this is a

shakedown and initially refuses to pay - but later, because it needs the work done, relents and agrees. Their (later) agreement is

a. unenforceable because EIEIO's performance was a preexisting duty.

b. unenforceable because McDonald's promise was illusory.

c. enforceable.

d. unenforceable because its performance is unforeseeably difficult.