If Stock A sometimes increases and sometimes decreases in value when Stock B increases in value at the same time, they are

If the price of a movie rises 3 percent and, as a result, the quantity demanded of video rentals increases 6 percent, then the cross elasticity of demand is

A) 2. B) 1/2. C) -1/2. D) -2. E) 9.

Assume the price elasticity of demand for a product is -4. In this case, the firm's optimal markup is (approximately):

A) 400 percent. B) 100 percent. C) 33 percent. D) 25 percent.