$$ \begin{cases} x_{R0} &= 0\ut{m} \\ x_{G0} &= 220\ut{m} \\ a_G &= Const. \\ a_R &= 0 \end{cases}$$ $$ \begin{aligned} S &= vt, \\ S_{R} &= v_{R}t \\ t &= \frac{S_{R}}{v_{R}} \end{aligned} $$ $$ (\text{Case A}) $$ $$ \begin{aligned} v_{RA} &= 20.0\ut{km/h} \\ &= 20.0\ut{km/h}\frac{1000\ut{m}}{1\ut{km}}\frac{1\ut{h}}{3600\ut{s}} \\ &= \frac{50}{9}\ut{m/s} \\ \end{aligned} $$ $$A\begin{cases} v_{..