A block of mass m is connected to a spring with spring constant k, and oscillates on

Question:

A block of mass m is connected to a spring with spring constant k, and oscillates on a horizontal, frictionless surface. The other end of the spring is fixed to a wall. If the amplitude of oscillation is A, derive a formula for the speed of the block as a function of x, the displacement from equilibrium. (Assume the mass of the spring is negligible.)