A boy weighing $\mathit{40}\mathit{ }\mathrm{kg}$ makes a high jump of $\mathit{1}\mathit{.}\mathit{5}\mathit{ }\mathrm{m}$. What is his potential energy at the highest point? (Take $g = \mathit{10}\mathit{ }\mathrm{m} {\mathrm{s}}^{-2}$)

Figure shows a ski -jump. A skier of mass $\mathit{60} \mathrm{kg}$ stands at A at the top of the ski-jump. He moves from A to B and takes off for his jump at B.
(i) Determine the change in the gravitational potential energy of the skier between A and B.
(ii) If $75\%$ of the energy calculated in part (i) becomes the kinetic energy at B, calculate the speed at which the skier arrives at B. (Take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)