Difficult mechanics problem?

a town committee is interested in redesigning some of the steep sections of a town. they hire an engineer to design the roads such that low powered cars can drive up the steep roads without slowing down. the engineer tests a low powered car with mass of 1200kg, and finds that it can accelerate on a level road from rest to 22m/s in 16s. using this data he makes plans for the new roads. what is the maximum steepness of the hills that he designs? ignore air resistance