The work done to push the box is equal to the product between the force and the distance through which the force is applied:
[tex]W=Fd[/tex]
In our problem, the force is F=1.4 N and the distance covered is d=150 m, so the work done by pushing the box is
[tex]W=Fd=(1.4 N)(150 m)=210 J[/tex]
