A pendulum is released from the $3$:$00$ o'dock position and it rotates clockwise untill it reaches the $9$:$00$ o'dock position where it stops, reverses direction and starts to rotate clockwise. Briefly explain what is happening to the kinetic energy as it moves from the $3$:$00$ o'clock postion to the $9$:$00$ o'clock position. Please answer the following questions.

a$.$ At what point $($or points$)$ is the kinetic energy of the pendulum equal to zero?

b$.$ At what point $($or points$)$ is the kinetic energy of the pendulum at it's maximum value?

c$.$ What force is responsible for the change in kinetic energy?