(3) [10 points] (a) Can a Giffen good be a normal good? Provide a formal (and short) argument to justify your answer. (b) Assume the production function f(x) has constant returns-to-scale. Show that for any given input prices w, the firm's marginal cost function is constant. Hint: Let x be the optimal input vector when the firm produces q = 1 and x2 be the optimal input vector when the firm produces q = 2. Compare to rl