Suppose Daria's demand is given by the function U(x,y) = 15x + 3y. You also know prices and income, given by Px=2, py=4, and (income) m=40. Using the marginal rate of substitution... O She would trade 15 units of good x for 3 units of good y; she prefers good y O She would trade 15 units of good x for 3 units of good y; she prefers good x O She would trade 1 unit of good x for 5 units of good y; she prefers good y O She would trade 1 unit of good x for 5 units of good y; she prefers good x