A 1.6-in. deflection of the second floor of a building is measured directly under a newly installed 8200-lb piece of rotating machinery which has a slightly unbalanced rotor. Assuming that the deflection of the floor is proportional to the load it supports, determine
(a) the equivalent spring constant of the floor system,
(b) the speed in rpm of the rotating machinery that should be avoided if it is not to coincide with the natural frequency of the floor-machinery system.