A local video store estimates their average customer's demand per year is Q = 20 - 4P, and knows the marginal cost of each rental is $1.

A local video store estimates their average customer's demand per year is Q = 20 - 4P, and knows the marginal cost of each rental is $1.00. How much should the store charge for an annual membership in order to extract the entire consumer surplus via an optimal two-part pricing strategy?