A Monopolist Faces Inverse Demand $P = 300 - 2 Q$

A monopolist faces inverse demand $P = 300 - 2 Q$ The monopolist's marginal revenue function is:

A) $M R = 300 - 2 Q$
B) $M R = 300 - Q$
C) $M R = 300 - 4 Q$
D) $M R = \frac { 300 } { Q } - 2$