3) Illustrate the following utility functions by sketching indifference curves in the X,Y space: (Need not be to scale as long as the general shape is reasonable) (a) U(X,Y) =

2X + 3Y (perfect substitutes)(b) U(X,Y) = X1/2Y 1/2 (Cobb-Douglas) (c) Derive the expression for the Marginal Rate of Substitution for the utility functions above.