Water flows in a horizontal rectangular channel. At a section, the velocity is $2\mathrm{.}5\frac{m}{s},$ width is $2\mathrm{.}3m,$ and the depth is $1\mathrm{.}5m.$ What is the water depth when a gradual expansion in the channel to a width is $3\mathrm{.}4m$ takes place? $[15]$