A two$-$hour duration storm event with uniform excess rainfall of $3cm$ occurred on a watershed. The ordinates of streamflow hydrograph resulting from this event are given in the table.

$\backslash$table$[[$Time $($hours$),0,1,2,3,4,5,6,7],[$Streamflow $(\frac{m^3}{s}),10,16,34,40,31,25,16,10]]$

Considering a constant base flow of $10\frac{m^3}{s},$ the peak flow ordinate $($in $\frac{m^3}{s})$ of one$-$hour unit hydrograph for the watershed is

$($a$)12\mathrm{.}66\frac{m^3}{s}$

$($b$)11\mathrm{.}66\frac{m^3}{s}$

$($c$)9\mathrm{.}66\frac{m^3}{s}$

$($d$)10\mathrm{.}66\frac{m^3}{s}$