How to calculate dampening coefficient?

[donkeycopter]

Homework Statement

A 100g mass moves on the end of a spring with force constant . It is released with an amplitude 0.2m. A damping force acts on the egg. After it oscillates for 5.00 s, the amplitude of the motion has decreased by 0.1m.Calculate the magnitude of the damping coefficient .

Homework Equations

I have no idea, research online doesn't show anything which seems relevant. I've found the equation: c=Fv (where c is the coefficient) but I don't see how that will be helpful.

 

[vela]

Doesn't your textbook discuss the damped harmonic oscillator? Surely there are equations in there that are relevant.