Suppose that a coal mine's workers can dig two tons of coal per hour and coal sells $10 per ton. The marginal revenue product of a coal mine is therefore $20 per ton. If the coal mine is the only hirer in the miners in a local area and faces a labor supply curve of the form this firm must recognize that it hiring decisions affect wages. Expressing the total wage bill as a function of . According the above mentioned information: a. Determine the marginal expense associated with hiring miners? b. How many labors that the firm should hire to maximize the profit? C. If market competitive price for hiring a labor is rather $20 per hour, what is labor hired at the market equilibrium, i.e. under competitive market price? d. Suppose the price of coal rises to $15. How would this affect the monopsonist hiring and the wage of coal miners