William W. answered • 03/11/19

Experienced Tutor and Retired Engineer

The function y = 4x is the outside radius and the function y = x^{2} is the inside radius of a washer cross-section that can be integrated from x = 0 to x =4

V = ∫A(x)dx = _{0} ∫^{4} π(r_{o}^{2} - r_{i}^{2})dx = _{0} ∫^{4} π[(4x)^{2} - (x^{2})]dx = 2048π/15 ≈ 428.9 units^{3}