A car of mass $1000\ \text{kg}$ climbs a long, straight slope that rises $1\ \text{m}$ for every $10\ \text{m}$ along the road ($\sin\theta = 0.1$). The engine can deliver at most $60\ \text{kW}$, and air and road resistance add up to a steady $500\ \text{N}$. Taking $g = 10\ \text{m/s}^2$, the greatest steady speed of the car up the slope is