4. (25 points) Consider an exchange economy with two goods (x and y) and two agents (a and b). Agent a has preferences represented by U.(Ta, ya) = Caya and endowment (wa, wa) = (2,3). Agent b has preferences represented by ub(b, yb) = min Xb, 2yb} and endowment (w., w.) = (6, 1). (a) Compute and draw the contract curve, the core, and all Walrasian equilibria. (b) Repeat part (a), but where agent a has preferences represented by max {Xa, 2ya}