3. Suppose that f : A ) B is a function and that U Q B. Dene f_1(U) = {a E A: f(a) E U}. a) Suppose that f : R > R is given by f($) = 1:2. Find f_1([0,4]) and f_1({07 107 5}). b) If U and V are any subsets of B, prove that f'1(U D V) = f'1(U) f'1(V)