4. We say that person n can afford to buy the pair (1, Ca2) at (P1. P2) if the price p = P1G1 + P2 G2 < P1Wn1 + PaWn2- (7) As is well-known, CE is a theory of allocations and relative prices. That is, there is no hope of determining both p1 and p. This follows because (P1. P2) and (p. P) with p = ap and p = ap, where a >0 determine the same affordable set. Exercise 8. Let (p, p) satisfy p Show that if (n1, Cn2) is affordable at (p1. P2), then (n1, Cn2) is affordable at (P1. P2)- = ap, and p, = ap, for any a > 0.