$1.$ Problema $2\mathrm{.}4.($p$\mathrm{.}114,$ Gupta$)$ At an upstream location on a river the flow is $75$ m$3/$s and at a downstream location it is $100$ m$3/$s$.$ In one hour the storage in the river reduces by $65,000$ m$3.$ If the upstream flow after one hour is $100$ m$3/$s$,$ what is the downstream flow after one hour? $($pg$.113,$ Gupta$).$