The rear side of a truck is open and a box of mass 20 kg is placed on the truck 4 m away from the open end. μ=0.15 and g = 10 m/s2. The truck starts from rest with an acceleration of 2 m/s2 on a straight road. The box will fall off the truck when it is at a distance from the starting point equal to x meter. Find value of x.