If e$=6\mathrm{.}00$V$,$ L$=8\mathrm{.}00$mH$,$ and R$=4\mathrm{.}00$ ohms in the circuit, what is the induced time constant in $($a$)$ the circuit? $($b$)$ Calculate the current flowing in the circuit at $250$ us after closing the switch. $($c$)$ What is the value of the steady$-$state current afterwards? $($d$)$ Find the time at which the current reaches $80\mathrm{.}0\%$ of its maximum value.