Assume there are 2 goods in the work: apple and raspberry. Say that geoffrey has a utility function for these goods, where r= quantity of raspberry, a =quantity of apple.
U = 4r + 3a
what is the marginal rate of substitution between the raspberry and the apples if geoffrey consumed 50 raspberries and 50 apples? what is the marginal rate of substitution if geoffrey consumed 100 raspberry and 50 apples? what do these answers to these question imply about the type of goods the apple and raspberry are for geoffrey?