20. Suppose that an individual has a constantMRS of shoes for sneakers of :(that is, he or she is always willing to give up 3 pairs of sneakers to get 4pairs of shoes). Then, if sneakers and shoes are equally costly, he or she will
* a. buyonly sneakers.
b. buy only shoes.
c. spend his or her income equally on sneakers and shoes.
d. wear sneakers only 3/4 of the time.