AL SHM

The equilibrium position occurs when the weight of the coin equals to the force given by the spring (note that at such position, the coin is NOT at stationary)

hence, 0.01g = 5.(Xo)
where g is the acceleration due to gravity, and Xo is the equilibrium position as measured from the original postion of the coin.
thus, Xo = 0.01g/5 m = 0.02 m (g is taken to be 10 m/s2)

Let h be the maximum displacement of the coin, by conservation of energy,
0.01g.h = (1/2).(5).h^2
solve for h gives h = 0.04 m

The coin will subsequently oscillates in simple harmonic motion, the amplitude of which is simply (0.04-0.02) m = 0.02 m