4.4 In the Mini-Case “Learning by Drilling,” an oil drilling firm’s average cost when working with production company M depends partly on its own cumulative drilling experience, N, and partly on the cumulative amount of drilling it has done jointly with production company M. Would an average cost curve AC = a + b1N- r + b2M- s exhibit such learning by doing? Explain. (Note:

a, b1, b2, r, and s are all positive constants.)