$7\mathrm{.}15$ Dry soil is characterized by ${}_x=25,p_x=1,$ and $={10}^{-4}(\frac{S}{m}).$ At each of the following frequencies, determine if dry soil may be considereda good conductor. a quasi$-$conductor, or a ben$-$boss dielectric, and then

$(1$i$)60$ Hz

$($b$)1$ kHz

$($c$)1$ MHz

$($d$)1$ GHz