Energy, work and power — practice question

A car with mass $800\text{ kg}$ travels along a straight road. It runs at constant speed $20\text{ m s}^{-1}$ on a horizontal stretch, and in that situation the engine delivers $P\text{ W}$. It also runs at constant speed $12\text{ m s}^{-1}$ on a stretch that slopes upward at $\sin^{-1}0.15$ to the horizontal, and there too the engine delivers $P\text{ W}$. On each stretch, a constant force of magnitude $R\text{ N}$ opposes the car’s motion.