Which of the Following Would Be Resolved by a Contract

Multiple Choice

Which of the following would be resolved by a contract and would not need the use of promissory estoppel? Assume that all facts given can be proven.

A) The contract called for the band to play for 3 hours,but the club owner agreed to pay the same price for only 2.5 hours of play.Later,the club owner sued for breach of contract.
B) The painter contracted with Frank to paint the kitchen for $400.When the painter found the job more difficult than he had expected,Frank said he would still pay $400 but that the painter didn't have to do all the work agreed upon; he didn't have to paint inside the cabinets.After the job was completed,Frank sued the painter for breach of contract.
C) The landlord forgave a tenant half of his October rent because the tenant had had an accident at work.Two days ago,the landlord sued for the unpaid rent on the grounds that his promise to forgive it was gratuitous.
D) Jon negotiated with the bank,which agreed to take $18 000 in full satisfaction of an overdue debt of $20 000.A week after Jon paid the $18 000,he was sued by the bank for the balance.
E) Kent loaned $3000 to Joan,who promised to pay back $3300 on January 3.Kent then called Joan and said that he would settle for $3000 if she would repay it that day,November 28.She paid on the 28th.On January 5,Kent sued Joan for the other $300.