John runs the only juice stall in the shopping centre. The following equations show

John's demand, marginal revenue, total cost, and marginal cost, respectively:

Demand: P = 20 - Q

Marginal revenue: MR = 20 - 2Q

Total cost: 5 + 4Q

Marginal cost: MC = 4

where Q is the quantity (bottles) of juice and P is the price.

a) How many bottles of juice does John sell? At what price are they sold? How much

profit does John make?

b) What is the price elasticity of demand at John's monopoly quantity and price?

c) Calculate the consumer surplus, producer surplus, total surplus, and deadweight

loss.