A body with a mass of m = 0.3 kg, attached to a spring with a stiffness of 18.33 N / m, oscillates with an amplitude

A body with a mass of m = 0.3 kg, attached to a spring with a stiffness of 18.33 N / m, oscillates with an amplitude of 1 cm.Find at what displacement of the body from the equilibrium position its acceleration is 0.3 m / s ^ 2, and determine the maximum value body speed.

For starters: 0.5 * k * A ^ 2 = 0.5 * k * x ^ 2 + 0.5 * m * v ^ 2.
2.x ^ 2 = (k * A ^ 2-m * v ^ 2) / k.
3.x = ((k * A ^ 2-m * v ^ 2) / k) ^ 0.5.
A = 0.08.
v = 0.03.
k = 0.1.
m = 0.4.