A Monopolist Faces Linear Inverse Demand $P = a - b Q$

Multiple Choice

A monopolist faces linear inverse demand $P = a - b Q$ and constant marginal cost, $c$ . The term $a$ increases by amount $\Delta a$ . By how much does the monopolist's optimal price increase?

A) $\Delta a$ .
B) $\Delta a / 2$ .
C) $\Delta a - c$ .
D) $\Delta a / b$ .