a) the slope of the total revenue curve is determined by the price of the goods produced b) the slope of the total revenue curve is explained by both a and b above. c) at higher levels of output, diminishing returns will cause total cost to slope downward steeply d) total revenue shown as a straight line sloping up indicates a perfectly competitive firm Refer to the diagram above. Which of the following explains the slope of the total revenue curve illustrated in this graph? Solution total revenue shown as a straight line sloping up indicates a perfectly competitive firm.