Please help with explanation and correct answer for number 20 and 21, thanks

20. [-/1 Points] DETAILS SESSCALCET2 7.3.510.XP.MI. Use the method of cylindrical shells to find the volume V generated by rotating the region bounded by the given curves about the y-axis. y = >, y = 0, X1 = 1, X2 = 2 V = Need Help? Read It Master It 21. [-/1 Points] DETAILS SESSCALCET2 7.3.513.XP. Use the method of cylindrical shells to find the volume V generated by rotating the region bounded by the given curves about the specified axis. y = 6e , y = 6e *, x = 1; about the y-axis Need Help? Read It