Answer
The impulse on the concrete is $~~(-8.25~kg~m/s)~\hat{j}$
Work Step by Step
In part (b), we found that the impulse on the ball is $~~(8.25~kg~m/s)~\hat{j}$
The impulse on the concrete is equal in magnitude, but opposite in direction, to the impulse on the ball.
Therefore, the impulse on the concrete is $~~(-8.25~kg~m/s)~\hat{j}$.
