If the price of firm A's cell phone service rises by 5 percent and the quantity demanded for firm B's cell phone service increases by 10 percent, we can say that
(A)demand for firm B is price elastic. (B)supply for firm B is price elastic. (C)firms A and B are substitutes because the cross-price elasticity is greater than zero. (D)firms A and B are complements because the cross-price elasticity is less than zero.
C