(exhibit: short-run costs) curve a crosses the average total cost

(Exhibit: Short-Run Costs) Curve A crosses the average total cost curve at:

(Exhibit: Short-Run Costs) Curve A declines from a cost of about $50 and a quantity of 1 to a cost of about $40 and a quantity of 2 (point F) at which time it rises again. The declining segment is due to ________ marginal returns, and the rising segment is due to _______ marginal returns.