7.21. A firm’s production function is Q ! min(K, 2L), where Q is the number of units of output produced using K units of capital and L units of labor. The factor prices are w ! 4 (for labor) and r ! 1 (for capital). On an optimal choice diagram with L on the horizontal axis and K on the vertical axis, draw the isoquant for Q ! 12, indicate the optimal choices of K and L on that isoquant, and calculate the total cost.