\(\left|\overrightarrow{\mathrm{a}}_{\mathrm{BA}}\right|=4 \mathrm{~m} / \mathrm{s}\)
\(\text { Apply }\left(\mathrm{v}^2=\mathrm{u}^2+2 \mathrm{as}\right)_{\text {relitive }}\)
\(\mathrm{O}=(40)^2+2(-4)(\mathrm{S})\)
\(\mathrm{S}=200 \mathrm{~m}\)
Remaining distance\(=300-200=100 \mathrm{~m}\)