In Figure 8.4, at 400 units of output: Figure 8.4 Two graphs stacked vertically-TC and TR are in the upper graph; a hill shaped total profit curve is in the lower graph; * is at the top of the hill; to the left of *, between zero and * total profit, quantity 200 is marked; to the right of *, between * and zero total profit, quantity 400 is marked In Figure 8.4, at 400 units of output: the last unit of output increases total profit. the slope of the total revenue curve is higher than the slope of the total cost curve. the last unit of output adds more to cost than to revenue. the last unit of output is worth producing to the firm because total revenue still exceeds total cost