A metal railing has the cross section shown below $($i$.$e$.$ a parrial circle ptus $3$ streight aldes$).$ a$)$ If $1$ section is $5\mathrm{.}5m$ long, find the lateral surfoce area in $m{m}^2$ and $m^2.$

b$)$ If $500$ such sections are to have their lateral surfoce areas pointed with $0\mathrm{.}15$ mmm thick coating, what volume $($in $m^3$ and litres$)$ of point is required?