If total profit is at a maximum, then average profit is zero

An increase in the price level results in a(n) ________ in the quantity of real GDP demanded because ________

A) decrease; a higher price level increases consumption, investment, and net exports. B) increase; a higher price level increases consumption, investment, and net exports. C) decrease; a higher price level reduces consumption, investment, and net exports. D) increase; a higher price level reduces consumption, investment, and net exports.

When two goods are perfect substitutes, averages are better than extremes, resulting a diminishing marginal rate of substitution.  

Answer the following statement true (T) or false (F)