. Suppose the economy is composed of N households, each differing only in its wealth level and family size. Let wi and s; denote household i's wealth and family size, respectively, and let xi(p, wi, si) and vi(p, wi, si) be the correspond- ing Marshallian demand and indirect utility function. Show that the aggregate demand only depends on price p, aggregate wealth w =Xiwi, and average family size s = y if every household's indirect utility function is given by: vi(p, wi,si) = a;(p) +b(p)wi + c(p)si