(a) (0.5 points) What kind of returns to scale does this production function exhibit? f( 21, Z2) = [min { z1, 3z2}]2 Oa. Constant returns to scale Ob. Decreasing returns to scale Oc. Increasing returns to scale Od. Cannot be determined from the given information (b) (1 point) At (21, Z2) = (4, 3), the marginal product of z1 is and the marginal product of Z2 is