Answer
(a) $10KJ$
(b) $-10KJ$
Work Step by Step
(a) The work done by the rope on the skier can be determined as
$W=Fdcos\theta$
$\implies W=F(vt)cos\theta$ because $d=vt$
We plug in the known values to obtain:
$W=(90.0)(14)(10.0)cos35^{\circ}$
$W=10,300J=10KJ$
(b) The force of water on the skier is in the opposite direction and it is due to the friction. Thus, this work done is equal to that done by the rope but in the opposite direction. That is, $W=-10KJ$
