An employer faces two types of employees. Regular workers are 70% of the population and generate $100,000 in productivity. Exceptional workers are 30% of the population and generate $120,000 in productivity. Employees know their types and reject salaries below their productivity. If the employer offers a salary equal to the average productivity in the population, what will be the employer's per-employee profit?

a. $10,000
b. $6,000
c. $0
d. $4,000