Answer
$\overline P=5.82\times10^4W$
Work Step by Step
According to Newton's 2nd law of motion, $$F=ma$$
We have $m=1.1\times10^3kg$ and $a=4.6m/s^2$, so $$F=5.06\times10^3N$$
The distance the vehicle has gone in $5s$: $$s=v_0t+\frac{1}{2}at^2=0+\frac{1}{2}\times4.6\times5^2=57.5m$$
The work done on the car is $$W=(F\cos\theta)s=Fs=2.91\times10^5J$$ ($\cos\theta=\cos0=1$ because $F$ is horizontal like the car's displacement.)
The average power generated by $F$ over $5s$ is $$\overline P=\frac{W}{t}=5.82\times10^4W$$
