A city planner is working on the redesign of a hilly portion of a city?

An important consideration is how steep the roads can be so that even low-powered cars can get up the hills without slowing down. It is given that a particular small car, with a m of 1130 kg, can accelerate on a level road from rest to 21 m/s (75.6 km/h) in 15.0 s. Using this data, calculate the maximum steepness of a hill.