The total revenue(price and quantity sold) is the amount of money the firm receives from selling its output.

The graph above shows how the price and the quantity are determined by the monopolist, who chooses the quantity where the marginal revenue (the additional revenue from selling one more unit) is equal to the marginal cost (the additional cost from producing one more unit).

This is the point M on the graph, where the MR and MC curves intersect.

The price is then given by the demand curve at that quantity, which is P1. The total revenue is the area of the rectangle with the base Q1 and the height P1, which is \(OQ_1 TP_1\)