$7\mathrm{.}3\mathrm{.}5.$ A discharge well penetrating a confined aquifer will be pumped at a rate of $800\frac{m^3}{h}r$ for two days, and then the pumping rate will be reduced to $500\frac{m^3}{h}r.$ The aquifer transmissivity is $40\frac{m^2}{h}r,$ and the storage coefficient is $0\mathrm{.}00025.$ Determine the drawdown at a location $50$ m from the pumped well three days after pumping has started.