This is about two exchange economies with L goods (and no firms). In economy 1, there are two consumers labeled A and B, who have utility functions and initial endowments (u_A, e_A) and (u_B, e_B) respectively. In economy 2, there are four consumers: the two consumers from economy 1 and two others consumers labeled a and b, who have utility function and endowment (u_a, e_a) = (u_A, e_A) and (u_b, e_b) = (u_B, e_B). Show that if utility functions are strictly quasi-concave and p^*, x_A^*, x_B^* is a competitive equilibrium in economy 1, then x_A^*, x_B^*, x_a^*, x_b^* with x_A^* = x_a^* and x_B^* = x_b^* is in the core of economy 2