For a falling$-$head permeability test, the following are given.

Length of the soil specimen $=510mm$

Area of the soil specimen $=22c{m}^2$

Area of the standpipe $=1\mathrm{.}3c{m}^2$

Head difference at time $t=0$ is $700mm$

Head difference at time $t=10$min is $300mm$

$($a$)$ Determine the hydraulic conductivity of the soil $($in $c\frac{m}{m}in).$

$c\frac{m}{m}in$

$($b$)$ What was the head difference $($in $mm)$ at time $t=5$min $?$

$mm$