6.15. Suppose that a firm’s production function is given by Q ! KL " K, with MPK ! L " 1 and MPL ! K. At point A, the firm uses K ! 3 units of capital and L ! 5 units of labor. At point B, along the same isoquant, the firm would only use 1 unit of capital.

a) Calculate how much labor is required at point B.

b) Calculate the elasticity of substitution between A and B. Does this production function exhibit a higher or lower elasticity of substitution than a Cobb–Douglas function over this range of inputs?