How to find the stiffness of beams?

I need to figure out the stiffness of these two beams. Both are 4 inches long and one has the dimensions 1/4" x 1/4" and the other has the dimensions 1/4"x1/8". The beam that is thinner is loaded on the face that is larger (ie. it's laying flat, the orientation that would make it structurally weaker). Both have a modulus of elasticity of 30e6 psi.