Answer
Please see the graph.
Work Step by Step
The average total cost curve intersects the marginal cost curve at the minimum point on the average total cost curve. The intersection of the marginal cost curve and the marginal revenue curve determines the quantity the monopolist will produce (and at what price will the monopolist sells the good).
The shaded rectangle is the profit for the monopolist. This rectangle is the difference between the price and the average total cost, and this difference is multiplied by the quantity (to get the profit).
