Suppose a Firm Is Using 100 Units of Labour and 50

Suppose a firm is using 100 units of labour and 50 units of capital to produce 200 completed client tax returns per day.The price of labour is $5 per unit and the price of capital is $2 per unit.The MP_L equals 5 and the MP_K equals 2.In this situation,the firm

A) is minimizing its costs.
B) should increase the use of both inputs.
C) could lower its production costs by decreasing labour input and increasing capital input.
D) could lower its production costs by increasing labour input and decreasing capital input.
E) should decrease the use of both inputs.