This is how you calculate the volume of an ellipsoid with the following equation.

rmax = 1;

V = 0;

step = 0.02;

A = 5;

B = 10;

C = 15;

for x= -5 : step : 5

for y = -10 : step : 10

for z = -15 : step : 15

if((x/A).^2 + (y/B).^2 + (z/C).^2) < rmax

V = V + step.^3;

end

end

end

end

disp(V)

it should spit out , approximately