Consider the following Scheme function fun:

$($DEFINE $($fun k x$)$

$($COND

$(($NULL$?$ x$)\text{'}())$

$))=((k(CARx)$

$($ELSE $($fun k $($CDR x$)))$

$)$

In each of the following cases, give the value of the expression and explain how it was derived.

$($a$)($fun $($:$8^{\text{'}}()\}$

$($b$)($fun $8\text{'}(48992$