Suppose that a consumer has the following utility function for chocolate ice cream and lemon sorbet: U(x,y) = 3x + 2y, where x is the quantity of chocolate ice cream consumed and y is the quantity of lemon sorbet consumed. If the consumer has a budget of $20 to spend on chocolate ice cream at $2 per unit and lemon sorbet at $3 per unit, what combination of chocolate ice cream and lemon sorbet will maximize utility?

a) x = 4, y = 2
b) x = 3, y = 4
c) x = 5, y = 1
d) x = 2, y = 3