Q$4.($b$)$ A commonly used shape for concrete lined canals, colled the standard lined trapezdidat canal sections, consists of trapezoidal section with each of its two corners being rounded off by a circular arc of a radius equal to the full supply depth. Determine the dimensions of such a standard lined trapezoidal canal to carry a disharge of $200$ m$^3/$s at a bed slope of $1$ in $4000.$ The side slopes ore $21$H:$1$V$,$ and Manning's n $0\mathrm{.}014.$ The