The figure above shows demand and marginal revenue for a single price monopoly.

At any price above $ demand is elastic.

Assume production costs are constant and equal to $9.00 (i.e., AC = MC

= $9).

Output is  units per day at a price of $  per unit.

Profit is $  .

Consumer surplus is $  .

If this market was perfectly competitive

, output would exceed

the single-price monopoly output by 

If this is a perfectly price discriminating monopoly at a constant cost equal to $4.50