Please help me with this

1. Suppose two roommates are thinking of buying a refrigerator for their apartment. Joe's utility function is: U, (R, M) ) = (1 + R)M, Kate's utility function is: Uk(R, MK) = (3 + R)MK R is equal to 0 or 1 (depending on whether a refrigerator is bought) and MJ and MK represent the amount of money they have to spend. Joe has a total wealth of $2,000 and Kate has a total wealth of $2,400. What is the maximum amount they would be willing to pay for a refrigerator