Problem $4(10$ points$)12\mathrm{.}13$

A $12-$ha catchment has pre$-$ and post$-$development times of concentration of $2\mathrm{.}5$ h and $1\mathrm{.}5$ h respectively,

and the pre$-$ and post$-$development runoff coefficient are estimated as $0\mathrm{.}3$ and $0\mathrm{.}6.$ respectively. The

IDG function is given by

i$=(7836)/(37\mathrm{.}7+0\mathrm{.}803$ t$)$mm$//$h

Where i is the rainfall intensity in mm$//$h and t is the duration in minutes. Use the modified rational

method to estimate the required storage so that the post$-$development peak runoff rate is equal to the

pre$-$development peak runoff rate. What is the ratio of the storage volume to the runoff volume? Please help, I've been stuck on this for hours.