$9\mathrm{.}16$ A dielectric material with $={}_o,=9{}_0=4\frac{S}{m}$ is placed between the plates of a parallel$-$plate capacitor. Calculate the frequency at which the conduction and displacement currents are equal.

$9\mathrm{.}46$ Find the instantaneous form for each of the following phasors:

$($a$)A_s=j10a_x+\frac{20}{j}{a}_y$

$($b$)B_s=j4e^{-j2x}{a}_x+6e^{+j2x}{a}_z$

$($c$)C_s=j2e^{-20z}{e}^{-j\frac{}{4}}{a}_z$