GR 8767# 34

Let the bottom edge of a rectangular mirror on a vertical wall be parallel to and h feet above the level floor. If a person with eyes t feet above the floor is standing erect at a distance d feet from the mirror, what is the relationship among h, d and t if the person can just see his own feet in the mirror?

The answer is A: t=2h and d does not matter

I feel it is like a physics problem. Do not know how to solve it.

Can anyone help me?

Thanks very much.