If an object on a horizontal, frictionless surface is attached to a spring, displaced, and then released,

Question:

If an object on a horizontal, frictionless surface is attached to a spring, displaced, and then released, it will oscillate. If it is displaced 0.120 m from its equilibrium position and released with zero initial speed, then after 0.800 s its displacement is found to be 0.120 m on the opposite side, and it has passed the equilibrium position once during this interval. Find
(a) The amplitude;
(b) The period;
(c) The frequency.