A solid cube of side c = 80 mm is attached as shown to cord AB. It is observed to spin at the rate ψ = 40 rad/s about its diagonal BC and to precess at the constant rate ? = 5 rad/s about the vertical axis AD. Knowing that b 5 30°, determine the angle u that the diagonal BC forms with the vertical. (Hint: The moment of inertia of a cube about an axis through its center is independent of the orientation of that axis.)