The hollow electrode in an ECM operation has outer diameter $=50$ mm and inner diameter $=20$ mm$.$The applied current $=1800$ amps and the voltage $=12$ volts.The specific removal rate of workmaterial is $3\mathrm{.}42$ x $10^(-2)$ mm$*/$A$-$s$).($a$)$ If the process is $80\%$ efficient, determine the rate of metal removal. $($b$)$ If the resistivity of the electrolyte $=140$ ohm$-$mm$,$ find the working gap.