A manager of a firm with market power faces the marginal revenue product and average revenue product curves shown below.The firm incurs weekly fixed costs of $1,800.The firm employs a single variable input,labor,which costs $600 per worker each week. Given the above,in profit-maximizing (or loss-minimizing)equilibrium,the firm's total variable costs are
A)$12,000.
B)$6,000.
C)$600.
D)$400.
E)none of the above