Suppose That Scott's Demand for a Public Good Is P

Suppose that Scott's demand for a public good is P = 7 - 0.3Q and that Mike's demand is P = 10 - 1.5Q.The marginal cost is $14.At the optimal quantity of provision,the marginal benefit of the public good is about

A) 1.67 units.
B) 3 units.
C) $1.67.
D) $3.00.
E) $14.