For the below MOS amplifier $($W$/$L$)1=($W$/$L$)2=5,($W$/$L$)3=($W$/$L$)4=1,($W$/$L$)5=4,($W$/$L$)7=28,$ ID$5=7$A$,|$n$|=|$p$|=0\mathrm{.}01$ V$-1,$ k$$n$=100$A$/$V$2,$ and k$$p$=40$A$/$V$2,|$VTP$|=1$V$.($a$)$ Find the value of $($W$/$L$)6$ if by design we set the DC potentials at the first$-$stage output nodes to be the same, that is VD$1=$VD$2.$ Hint: if VD$1=$VD$2$ is required by design, then VSG$6=$VSG$3$ since VSG$6=$VDD$-$VG$6=$VDD$-$VD$2$ as VD$2=$VG$6,$ and VSG$3=$VDD$-$VD$1$ as VD$1=$VG$3($b$)$ Find the small$-$signal gain $($vo$/$vi$)$