Determine the location where E$\_$x is a positive maximum when t$=10^-4?$ given A uniform plane wave with E$=$a E$,$ propagates in a lossless simple medium with $($permitinity$+4,$ permeability $=1$ in the $+$z direction $.$ Assume the Ex is a sinusoidal with frequency $=100$MHz and has a value of $10^-4($V$/$m$)$ at t$=0$ and z$=1/8($ m$).$