Mostly need help with C, D, and E.

The radius of a sphere is 3 inches. which represents the volume of the sphere?

Someone me i need with this stuff

Barrett is comparing the membership fees for two museums.the art museum charges a one-time fee of $8.25 plus $2.25 per month. the science museum charges a one-time fee of $10.75 plus $3.50 per month. how much does barrett save by joining the art museum instead of the science museum?