Suppose Sammie Wall currently has a monopoly on widgets. The inverse demand function for the only customer interested in widgets is [P=40-6Q] and the cost to produced widgets can be described by the following cost function: [C=10+2Q^2] . If Sammie decides to open a membership warehouse that only sells widgets, how much would she charge for a membership in order to maximize profits? (Give only the numerical answer below with no $.)