$1.$ Sometimes the substrate is connected to a voltage called the substrate bias to alter the threshold of the NMOS transistors. If the threshold of an NMOS transistor is to be raised, should a positive or negative bias be used? $[2$pts$]$

$2.$ With technology scaling does recurrent or non$-$recurrent engineering costs increase? Which one becomes more dominant? Justify your answer by elaborating with a scenario or example.$[3$pts$]$

$3.$ Why is polysilicon not used in routing? $[4$pts$]$

$4.$ An important component of IC layout is design rules. What do design rules indicate? $($within the manufacturing process$)[3$pts$]$

$5.$ Give three $(3)$ good reasons to why CMOS logic is preferred in digital VLSI Design $($e$.$g$.$ as opposed to NMOS$-$only logic$).[3$pts$]$