A Multi- Plant Firm Has Three Plants

A multi- plant firm has three plants. At its current production levels, the marginal cost of production is $1.50 at plant 1, $1.50 at plant 2, and $1.50 at plant 3. The firm's overall marginal cost of production is _______.

A) $7.50
B) $1.50
C) $4.50
D) $3.00