A block of mass 0.4 kg on a horizontal surface is attached to a horizontal spring of negligible mass. The other end of the spring is attached to a wall, and there is negligible friction between the block and the horizontal surface. The center of mass of the block is stretched a horizontal distance x=0.25 beyond its equilibrium position and released from rest such that the block-spring system undergoes simple harmonic motion. A graph of the spring potential energy of the block-spring system as a function of the horizontal position of the center of mass of the block is shown. The positive direction is considered to be to the right. (a) On the grid below, sketch a graph of the force exerted by the spring on the block as a function of the block’s horizontal position.