JEE Advanced 2018 Paper 2

A solid horizontal surface is covered with a thin layer of oil. A rectangular block of mass m=0.4kg is at rest on this surface. An impulse of 1.0Ns is applied to the block at time t=0 so that it starts moving along the x-axis with a velocity v(t)=v0e−t/τ,where v0 is a constant and τ=4s The displacement of the block, in metres, at t=τ is_____.
Take e−1=0.37