You try to keep a box lifted by pushing it up against a wall $($horizontally$)$ but it starts slipping. You continue to push with a constant force of $150$ N as it falls on a countertop. The mass of the box is $50$ kg $.$ The coefficient of kinetic friction is $0\mathrm{.}2.$ The box starts out $0\mathrm{.}5$ meters above the countertop. Use the work energy theorem to find the velocity with which it hits the surface.