Answer
$\Delta x_{bs} = 40~m$
Work Step by Step
In part (b), we found that the time of the ball's flight is $4.0~s$
Note that $v_{0x} = 10~m/s$ is the ball's velocity relative to the sled.
Therefore, the horizontal displacement $\Delta x_{bs}$ is $(10~m/s)(4.0~s)$ which is $40~m$
$\Delta x_{bs} = 40~m$
