Assume that a shaker is excited to vibrate using the following signal, z(t) = 5 sin(9000t) + 2 sin(18000ft) where z is the vertical displacement in mm. Knowing that the fundamental frequency of each accelerometer is 18000 Hz and the damping ratio is 0.80, answer the followings: a) Calculate the maximum dynamic error in the z measurement. b) Plot the amplitude spectrum of the signal. c) Choose a sampling frequency (fs) (in Hz) such that the shaker vibration can be acquired accurately. d) Determine the period of the signal.