$$\put \begin{cases} m:\text{man}\\c:\text{car}\\\end{cases} $$$$ \begin{cases} m_mg&=850\ut{N}\\m_cg&=1700\ut{N}\\v_{ci}&=18.2\ut{m/s}\\v_{m\larr c}&=-4.00\ut{m/s}\end{cases} $$$$ \begin{aligned}v_{m\larr c}&=v_m-v_c\end{aligned} $$$$\Delta \Sigma \vec p=0,$$$$\vec p_i=\vec p_{mf}+\vec p_{cf}$$$$(m_m+m_c)v_i=m_mv_m+m_cv_c$$$$ v_c=v_i-\frac{m_m }{m_c+m_m}v_{m\larr c}$$$$ \begin{aligned}\Delta v_..