Answer the question based on the following information for a public good. Peand Pyare the prices that individuals A and B are willing to pay for the last unit of a public good, rather than do without it. These people are the only two members of society Q 1 2 3 Pa $3 2 Pb $5 4 3 2 1 4 5 1 If the marginal cost of producing this good at the optimal quantity is $8. the optimal quantity must be