3. (Volume Derivations) Derive the volume of a sphere with radius r using the disk method by integrating over either the x- or y-axis. Use the picture to help gather your thoughts. (Hint: The equation for a sphere is given by x2 + y = r, where r is the radius of the circle) 4. (Aircraft Fuel tanks) Fuel tanks on the wing of a jet aircraft is formed by revolving the region bounded by the function: 1 f(x) = x25-x2 About the x-axis between [0,5] where x and f(x) are measured in feet. Find the tank's volume. Provide a rough sketch of the shape of the tank. Interpret your answer accordingly.