如果铅笔和钢笔是替代品，铅笔价格上升引起钢笔的需求减少。

Suppose that all consumers view red pencils and blue pencils as perfect substitutes.Suppose that the supply curve for red pencils is upward sloping.Let the price of red pencils and blue pencils be p_rand p_b.What would happen if the government put a tax only on red pencils？

A.A.14支

B.B.16支

C.C.18支

D.D.20支

A.14支

B.16支

C.18支

D.20支

A.6.3÷10×1000

B.6.3×10÷1000

C.6.3×10×1000