Answer
The work done by the wall is $-4170~J$
Work Step by Step
The work done by the wall on the skater is equal to the skater's change in kinetic energy. We can find the work done by the wall:
$Work = KE_2-KE_1$
$Work = 0-\frac{1}{2}mv^2$
$Work = -\frac{1}{2}(69.0~kg)(11.0~m/s)^2$
$Work = -4170~J$
The work done by the wall is $-4170~J$
