For the differential equation $...$

y $($t$)+3$t

$2$y $($t$)+2$y$($t$)=6$u$($t$)7$u$($t $2),$ select the

best description of its classification:

$($a$)$ Non$-$causal

$($b$)$ Linear and time$-$invariant

$($c$)$ Time$-$invariant

$($d$)$ Nonlinear

$($e$)$ Linear and time$-$varying

$($f$)$ None of the above