Answer:
the amplitude(x) of the motion  = 0.078 m
Explanation:
the maximum kinetic energy occurs at maximum speed, that is:
Kmax = 1/2×m×(v^2) = 1/2×(0.20)×(1.9)^2 = 0.361 J
then, in a simple harmonic motion, energy is conserved, the sum of kinetic energy and potential energy is always constant:
then, the maximum potential energy in the spring is given by:
Umax = 1/2×k×(x^2) , where x is the amplitude of the oscillation.
     =  1/2×(120)×(x^2)
then by conservation of energy:
 Kmax = Umax
0.361 J = 60×x^2
   x^2 = 6.02×10^-3
     x = 0.078 m
Therefore, the amplitude of the motion is 0.078 m. Â
