PLS HELP ASAP WITH PART B, C, & D PLS PLS

Cd is the perpendicular bisector of both xy and st, and cy=20. find xy.

Find the solution on the interval [0, 2pi)

To keep cylindrical tanks from tipping over, a designer is planning to enlarge the original area of the base by 50%. the new tank should have the same volume as the original. how should the designer change the height of the tank? a: make it 50% taller than the height of the original tank. b: make it 6623% taller than the height of the original tank c: make it 3313% shorter than the height of the original tank d: make it 50% shorter than the height of the original tank.