[" A car starting from rest accelerates at the rate "f" through a "],[" distance "s," then continues at a constant speed for time "t" and "],[" then decelerates at the rate "f/2" to come to rest.If the total "],[" distance travelled is "15" ,then "],[[" (a) "s=ft," (b) "s=(1)/(6)ft^(2)],[" (c) "s=(1)/(72)ft^(2)," (d) "s=(1)/(4)ft^(2)]]