The distance s metres from a fixed point of a vehicle travelling in a straight line with constant acceleration, a m/s2, is given by s=ut + 1/2 at2, where u is the initial velocity in m/s and t the time in seconds. Determine the initial velocity and the acceleration given that s=42m when t =2 s and s=144m when t =4 s. Find also the distance travelled after 3 s