Figure 21-01 A graph shows Quantity of Output on the horizontal axis and Cost on the vertical axis. There are four curves drawn on the graph, as follows reading from left to right: ? Curve D slopes downward, becoming less steep as quantity of output increases ? Curve A starts out downward sloping then becomes upward sloping as quantity of output increases ? Curve C starts out steeply downward sloping, then becomes upward sloping after it intersects curve A ? Curve B lies above curve C at all levels of output. It starts out steeply downward sloping, then becomes upward sloping after it intersects curve A. Refer to Figure 21-1. Curve D is a(n) __________ cost curve. You Answered marginal Correct Answer average fixed average total average variable