Answer
See the graph below.
Work Step by Step
We have here 4 stages of motion. The ball is rolling without friction at a constant speed toward the wall until it hits it. And then the ball bounces back at the same speed but in the opposite direction. Then the ball speeds up while moving down the incline, and the only cause of its speeding up is its own weight component in the direction that is parallel to the inclined surface.
Then the ball reaches the ground and continues moving at a constant speed that is greater than the initial speed.
The red vertical line in the figure below, in the $a_s$ versus $t$ graph, represents the bounce acceleration due to the ball. It is too big since the ball is assumed to not lose any speed which means that the collision is assumed to be perfectly elastic.
