Forces and equilibrium — practice question

A van with mass $4500\,\text{kg}$ is pulling a trailer whose mass is $350\,\text{kg}$ along a straight horizontal road. The van and trailer are joined by a light rigid tow-bar that is parallel to the road. Resistance forces of $X\,\text{N}$ act on the van and $120\,\text{N}$ act on the trailer. The driving force provided by the van’s engine is $2500\,\text{N}$. The tension in the tow-bar is $T\,\text{N}$, and the van’s acceleration is $0.4\,\text{m s}^{-2}$.