need help with 13 a to d and 15 a

In Exercises 13-16, find the volume of the s erated by revolving the region bounded by the the given equations about the indicated lines. 13. * = Vx, y = 0, x = 4 (a) the x-axis (b) the y-axis (c) the line x = 4 (d) the line x = 6 14. y = 2x2, y = 0, x = 2 (a) the y-axis (b) the x-axis (c) the line y = 8 (d) the line x = 2 15. y = x2, y = 4x - x2 (a) the x-axis (b) the line y = 6 16. y = 6 - 2x - x2, y = x+6 (a) the x-axis (b) the line y = 3 In Exercises 17-20, find the volume of the solid erated by revolving the region bounded by the graphs the given equations about the x-axis. 17. y = xV4 - x2 , y = 0 18. y = 2x2/3 - x, y = 0 x 19. y = =, y = 0, x = 1, x = 4 20. y = - 3 x + ] ' y = 0, x = 0, x =8