In a simple harmonic motion system, a mass is attached to a spring and oscillates back and forth. Which of the following statements about the system is incorrect?

a$.$ The velocity of the mass is maximum when it passes through the equilibrium Position.

b$.$ The acceleration of the mass is maximum when the mass is at the maximum displacement from equilibrium.

c$.$ The total mechanical energy of the system remains constant throughout the motion

d$.$ The restoring force on the mass is constant throughout the motion.