haha its not that hard, think about area of a circle...its pi*r^2 (the same as pi*r*r).
so what is r, the radius, how many different radii are there in an ellipse? the answer is two, so what would a and b be?
each of the radii of course, which are known as the semi major and semi minor.
so its pi * semi major (a aka bigger radius) * semi minor (b aka smaller radius)
you can switch them around i think...
so it could be:
pi * semi minor * semi major.
hope that helped.
ps. you DON'T have to square the semi minor or semi major. that is a common error when there is errors.