Let W and L denote the wage and the amount of labor employed, respectively. A firm faces the labor supply curve L = 2W - 6 and the marginal product of labor is given by MPL = 20 - L. The firm sells its output in a perfectly competitive market at $0.50 each.

(a) If this labor market is perfectly competitive, find the equilibrium employment, the equilibrium wage, and the number of unemployed people.

(b) Suppose that the government imposes a minimum wage of $7. Find the equilibrium employment and the number of unemployed people.

(c) If this labor market is controlled by a non-discriminating monopsonies, find the equilibrium employment, the equilibrium wage, and the number of unemployed people.

(d) If this labor market is controlled by a non-discriminating monopsonies and the government imposes a minimum wage of $7, find the equilibrium employment and the number of unemployed people.