Outflow from orifice

Problem $1$ The $1-$m$-$diameter cylindrical tank is initially filled with gasoline at $20C.$ There is a $2-$cm$-$diameter orifice in the bottom. If the orifice is suddenly opened, estimate the time for the fluid level $h(t)$ to drop from $2\mathrm{.}0$ to $1\mathrm{.}6m.$ Suppose the value of the ontflow velocity coefficient of $0\mathrm{.}62.$

Ansfer: Outflow time is $271\mathrm{.}8s.$