$6\mathrm{.}7)$ For a falling$-$head permeability test, the following are given: Length of specimen $=380$ mm $,$ area of specimen $=6\mathrm{.}5cm2,$ and $k=0\mathrm{.}175c\frac{m}{m}in.$ What should the area of the standpipe for the head to drop from $650$ cm to $300$ cm in $8$ min $?$