Suppose we know little about the strength of materials but are told that the bending stress  in a beam is proportional to the beam half thickness y and also depends on the bending moment m and the beam area moment of inertia i. we also know that, for the particular case m = 2900 in·lbf, y = 1.5 in, and i = 0.4 in4 , the predicted stress is 75 mpa. using this information and dimensional reasoning only, find, to three significant figures, the only possible dimensionally homogeneous formula  = y f(m, i).