A solid is formed by revolving the region under a positive function y=f(x) on [0,2] about the x-axis, producing volume V1. A second solid is formed by revolving the region under y=21f(x) on the same interval about the x-axis, producing volume V2. Which of the following describes the relationship between V1 and V2?
a) V2=81V1
b) V2=21V1
c) V2=41V1
d) V2=V1