What Is The Formula To Use?

[ChipSkylark3220]

A spring is suspended from a ceiling with no mass attached. Then, a mass m1 is attached to the bottom and allowed to fall. The spring has spring constant k.

a. How long will it take before the mass reaches the top again?

b. How far down will the mass get, measured from its initial position?

c. When the mass is at the very bottom of its oscillation, a second mass m2 is added. How far is the new lowest point of the oscillation?

d. Does the top of the oscillation change after m2 is added? If so, how far from the initial position will the top point be, and will be it be above or below the initial position of mass m1?

For A I got T=2pi x sqrt(m1/k) and B is x=2mg/k.
For C do I just add the masses together? Would it be 2x=2(m1+m2)g/k
and not sure about D