Question

The base of a solid is a region bounded by the curve (x^2/64) + (y^2/16) = 1. Find the volume of the solid if every cross section by a plane perpendicular to the major axis (x-axis) has the shape of an isosceles triangle with height equal to 1/4 the length of the base.

* I need help finding the equations used to calculate the areas and base of the cross sections