If the DC bias voltage, Vd$,$ across a reverse biased linear PN junction is

equal to $-3\mathrm{.}6$V then what is the capacitance of this junction in femto Farads?

Assume that Cj$0$ for the junction is equal to $988\mathrm{.}6$ fF$.($Note that $1$ fF $=1$ femto

Farad $=1$ x $10^-15$ F$.)$ Also assume that the built$-$in voltage for this junction is

equal to $842$mV$.$