ECONOMICS HOMEWORK HELP?!?!?!?!?!?!?

A factory employing labor as a variable input, is unionized. The new union wage contract increases hourly wages paid to workers by 20 percent. If there is no shift in the average product of labor curve after the union contract takes effect, the average variable cost curve for output in the factory will.... a. stay the same. b. shift up. c. shift down. d. More information is needed to answer this question.