Answer
$\overline P=2975W$
Work Step by Step
Since tension in the cable is not a conservative force, $$W_{nc}=E_f-E_0$$ $$W_T=\frac{1}{2}m(v_f^2-v_0^2)+mg(h_f-h_0)$$
The skiers are lifted at constant speed, so $v_f-v_0=0$. Therefore, $$W_T=mg(h_f-h_0)$$
The total mass of 4 skiers $m=4\times65=260kg$, $g=9.8m/s^2$ and $h_f-h_0=140m$
$$W_T=3.57\times10^5J$$
The lift goes for $t=2min=120s$, so $$\overline P=\frac{W_T}{t}=2975W$$
