Newton's laws of motion — practice question

A lorry with mass $12\,000\,\text{kg}$ travels up a straight hill that is $500\,\text{m}$ long, beginning at the foot of the hill with speed $24\,\text{m s}^{-1}$ and arriving at the top with speed $16\,\text{m s}^{-1}$. The summit of the hill is $25\,\text{m}$ higher than the level at the bottom. The resistance to motion of the lorry is $7500\,\text{N}$.