Vibration problem with springs

I am looking for the solution of this problem. Also, I would like to know which answer is correct out of the four that I provide.

Single degree of freedom vibration problems with forcing functions

Need help with this Undergraduate problem where two dampers are in series. For a vertical spring/damper system with mass (M) and a harmonic forcing function, Fmax Cos [omega x t] , two dampers are in series with coefficients, C1 and C2, and a single spring with constant, k. Determine the amplitude of the steady-state displacement. Determine the critical damping coefficient, Ccr.

Longitudinal versus Transverse Vibrations in a bar

A 48 inch long by 2 inch diameter round steel rod (E=30e6 psi, density=0.28 lb/in3) is fixed at one end and free at the other. If the rod is struck transversely so that there is both a longitudinal and transverse wave generated, how long does it take for each wave to complete a cycle? If you wanted to record 5 cycles for each type of wave, how long would you set your instrument's recording time for each wave type?

Mechanical Vibration.

1)The following data on the value of a variable: 2.3, 3.5, 3.5, 4.9, 3.7, 0.7, 4.1, find the average value, the mean-square value, the variance, and the coefficient of variation. (Mechanical Vibration) Please solve this problem

Question 3 Only

Please see the attached. I am looking for help with question 3 ONLY in this posting. The other questions have been posted separately. This is from the book Mechanical Vibration, (ISBN 0-13-948373-X), By Haym Benaroya, year 1998. An m-c-k system is tested to determine the value of c. Assume k=10lb/ft and m=2slug. If the vibrational amplitude is observed to decrease 33% of its initial value after two consecutive cycles, what is the value of c? Please see attached.