Problem 3 (25 pts) Explain your answers! (uses material from March 1 and 3) A firm has the production function f(21, 12) = 1yr, where r, and 12 are the input quan- tities. (a) Write the equation of the isoquant for output level 12 and find three points on it. Is the isoquant negatively sloped? Explain briefly why. (b) Find the marginal product of each input. Are the marginal products decreasing (dimin- ishing) in the input quantity? (c) Does the firm have decreasing, increasing, or constant returns to scale