Suppose the firm currently employs 500 workers and 100 units of capital and that the following relationship holds: MPL/W= 12/3=4 and MPK/C= 15/3=5. MPL and MPK are the marginal products of labor and capital, respectively. W is wage and C is the per unit cost of capital. Prove that the firm is not at an equilibrium mix of labor and capital by clearly explaining how there is an opportunity to produce more of the good it is producing now at the same cost.