Since x= 5 is a vertical line, a point rotated around it will form a horizontal circle. A point on the line x= 0 forms a circle of radius 5 and a point on $\displaystyle y= x^3$, which is the same as [tex]x= y^{1/3} forms a circle of radius 5- x= 5- y^{1/3}. What is the area of the region between those circles? Think of each as a thin disk of thicknes dy and "add" them all up.