Lou’s preferences over pizza (x) and other goods (y) are given by U(x, y)

Lou’s preferences over pizza (x) and other goods (y) are given by U(x, y) = xy, with associated marginal utilities. His income is $120.
a) Calculate his optimal basket when Px = 4 and Py = 1.

b) Calculate his income and substitution effects of a decrease in the price of food to $3