#### Answer

The work done by the pushing force $P$ is $+1120J$.
The work done by kinetic friction $f_k$ is $-943.25J$.
The work done by the $mg$ and $F_N$ is $0$.

#### Work Step by Step

The four forces that act on the box are the pushing force $P$, kinetic friction $f_k$, gravitational force $mg$ and normal force $F_N$
Since there is no vertical displacement, the work done by $mg$ and $F_N$ is 0.
1) Pushing force $P$
$P=160N$, $s=7m$, the angle $\vec{P}$ makes with the box's displacement $\theta=0^o$. The work done by $P$ is $$W=Ps=+1120J$$
2) Kinetic friction $f_k$
We have $f_k=\mu_kF_N=\mu_kmg$ (since there is no vertical acceleration)
So, $f_k=0.25\times55\times9.8=134.75N$
$f_k$ opposes the motion, so the angle $\vec{f}_k$ makes with $\vec{s}$ is $\theta=180^o$
The work done by $f_k$ is $$W=(f_k\cos180)s=-943.25J$$