2A, If B/A > 2 U'(A, B) = Max {A, B} IF B/AE [1/2,2] 2B If B/A 2 A+ B U"(A, B) = IF B/AE [1/2,2] 2B, If B/A 0 and P,>0 be the price of good A and Good B Respectively. Let I > 0 where I belong to income. For 1 = 1,2, let hi(P.,P ,U) denote the set of solutions of the problem: Choose A > 0 and B > 0 to minimize P. A + P,B subject to ui(A, B) 2 U. Let ei(P., P., U) = P.A + PB, where (A,B) E hi(P., P., U)