A rectangular channel $5\mathrm{.}0m$ wide is laid on a slope of $0\mathrm{.}004.$ The roughness coefficient $n=0\mathrm{.}015.$ Find the normal depth for discharge $20\frac{m^3}{s^2}$ through this channel

m $1\mathrm{.}24.a$

$1\mathrm{.}134\mathrm{.}6$

$1\mathrm{.}114\mathrm{.}6$

$1\mathrm{.}014.d$