Suppose Island Bikes, a Profit-Maximizing Firm, Is the Only Bike

Multiple Choice

Suppose Island Bikes, a profit-maximizing firm, is the only bike rental company in a small resort town. The marginal cost to Island Bikes of renting out a bike is $3, and Island Bikes has no fixed costs. Each day Island Bikes has six potential customers, whose reservation prices are listed in the table.  
$$\begin{array} { | c | c | } \hline \text { Custamer } & \begin{array} { c } \text { Reservetion Price } \\\text { (\$ /Rental) }\end{array} \\\hline \mathrm { A } & 22 \\\hline \mathrm { B } & 16 \\\hline \mathrm { C } & 12 \\\hline \mathrm { D } & \mathrm { 8 } \\\hline \mathrm { E } & 6 \\\hline \mathrm { F } & 4 \\\hline\end{array}$$ What is the socially optimal number of bikes for Island Bikes to rent out each day?

A) 6
B) 5
C) 4
D) 3