An NMOS device has parameters VT N $=0\mathrm{.}8$ V$,$ L $=0\mathrm{.}8$m$,$ and k n $=120$A$/$V$2.$ When the transistor is biased in the saturation region with VGS $=1\mathrm{.}4$ V$,$ the drain current is ID $=0\mathrm{.}6$ mA$.($a$)$ What is the channel width W$?($b$)$ Determine the drain current when VDS $=0\mathrm{.}4$ V$.($c$)$ What value of VDS puts the device at the edge of saturation