Consider a firm with monopoly power that faces the demand curve $$P=100-3 Q+4 A^{1 / 2}$$ and has the total cost function $$C=4 Q^{2}+10 Q+A$$ where $A$ is the level of advertising expenditures, and $P$ and $Q$ are price and output.
a. Find the values of $A, Q,$ and $P$ that maximize the firm's profit.
b. Calculate the Lerner index, $L=(P-M C) / P$, for this firm at its profit-maximizing levels of $A, Q,$ and $P$