Refer to the Following Figure

Refer to the following figure:

The figure above shows the demand and cost conditions for a firm with two plants.
-How should the firm allocate total output between the two plants in order to maximize profit?

A) produce 10 units in plant 1, 20 units in plant 2
B) produce 30 units in plant 1, 20 units in plant 2
C) produce 40 units in plant 1, 40 units in plant 2
D) produce 40 units in plant 1, 50 units in plant 2
E) produce 55 units in plant 1, 60 units in plant 2