In the two-period intertemporal consumption model, if MRS = C2/(4C1), r= 5%, Y1 = 50 and Y2 = 105, the optimal consumption combination
a) is C1 = 50 and C2 = 105
b) is C1 = 30 and C2 = 30
c) is C1 = 30 and C2 = 126
d) Depends on whether the consumer has a borrowing constraint