What is the volume of a hemisphere with a diameter of 7.1 ft, rounded to the nearest tenth of a cubic foot?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

Use the method of cylindrical shells to find the volume v generated by rotating the region bounded by the curves about the given axis.y = 7ex, y = 7e^-x, x = 1; about the y-axis

An elevator travels 310 feet in 10 seconds. at that speed, how far can't his elevator travel in 12 seconds?