Answer:
a). C = b/2 and C = b/4
b). 
c). m = 63.4 kg (approx.)
Explanation:
Ex. 2.4.4
The total force acting on mass m is
, where x is the displacement from the equilibrium position.
The equation of motion is 
or
or
, where
The solution is
, where A and Ф are constants.
A is amplitude of motion
is the angular frequency of motion
Ф is the phase angle.
Now, 
or 
Given 
a). 
b).
or 
Ex. 2.4.5
a). Total force acting on the mass m is 

The equation of motion is 
or
, angular frequency of the undamped oscillation.
γ = b/2m is called the damping coefficient (γ=C)

for 1 kg weight (= 9.8 N),
= 1.1 Hz
k = 4 x (3.14)² x (9.8) x 1.1² = 4.6 x 10² N/m
For 2 kg weight (= 19.6 N),
= 0.8 Hz
k = 4 x 9.8596 x 2 x 9.8 x 0.8² = 5 x
N/m

or 
γ = b/2 (for 1 kg) and γ = b/4 (for 2 kg)
C = b/2 and C = b/4
b). 
For two particle problem,


where, μ is the reduced mass.
This time period is same for both the particles.
c). 
( approx.)