$($Chap $3$ #$7)$ A constant$-$head permeameter has a cross$-$sec$8$onal area of $78\mathrm{.}5$ cm$2.$ The sample is $23$ cm long. At a head of $3\mathrm{.}4$ cm$,$ the permeameter discharges $50$ cm$3$ in $38$ s$.$