P $3.$ An NMOS transistor, operating in the triode region with vDS$=1$ V$,$ is found to conduct $0\mathrm{.}6$ mA for vGS $=2$V and $1\mathrm{.}6$ mA for vGS $=4$ V$.$ a$)$ What is the apparent value of threshold voltage Vt $?$ b$)$ If k$$n $=0\mathrm{.}5$ mA$/$V$2,$ what is the device W$/$L ratio? c$)$ What current would expect to flow with vGS $=3$V and vDS $=0\mathrm{.}15$V$?$ d$)$ If the device is operated at with vGS $=2\mathrm{.}25$V$,$ at what value of vDS will the drain end of the MOSFET channel just reach pinch off, and what is the corresponding drain current?