Answer: $19,800
Explanation;
The Monopolist will maximize output at the point where Marginal Revenue equals Marginal Cost because at this point all resources are being fully utilized.
Total Cost = Average Total Cost * Quantity produced
At the point where MR=MC, the quantity produced is 1,100 units.
The Average Total Cost tallying with this is $18 per unit.
Total Cost = 18 * 1,100
= $19,800