The intensity-duration relationship for a rainfall on a rectangular plot $\text{ABCD}$ of area $7$ \text{ha} ($1 \mathrm{~ha}=10^{4} \mathrm{~m}^{2}$) can be modelled by the following equation:
\[
I=\frac{25}{(t+10)}
\]
where $I$ is rainfall intensity (in $\mathrm{cm} / \mathrm{h}$ ), and $t$ is the duration (in minutes) of rainfall. The average runoff coefficient over the area is $0.60$. The time of entry (in minutes) to the outfall from the corners $\mathrm{A}, \mathrm{B}, \mathrm{C}$, and $\text{D}$ is $10,20,15$ and $25$, respectively.
The design flowrate (in $\mathrm{m}^{3} / \mathrm{h}$ ) of the storm-sewer at the outfall is $\_\_\_\_$ (in integer).
