A 30g bullet with a horizontal velocity of 500m/s comes to a stop 12 cm within a solid wall. a) what is the change in its mechanical energy?

A 30g bullet with a horizontal velocity of 500m/s comes to a stop 12 cm within a solid wall. a) what is the change in its mechanical energy? b) What is the magnitude of the average force from the wall stopping it? a) what would I use of the equation? Can you please explain what i would do? I am confused b)Would I use F= ma?a) The original mechanical energy is the kinetic energy. It goes from (1/2) M Vo^2 to zero. Vo is the initial velocity, 500 m/s b) (average Force) x (stopping distance) = mechanical energy loss Solve for the average force