$A=\{w$:$w=a^n$:$nis$ a prime number $\}$

$B=\{w$:$w=$ and $M()$ halts $\}$

$C=\{w$:$w=a^k{b}^m\}$

$D=\{w$:$w=$ and $M()$ doesn't halt $\}$

$E=\{w$:$w=a^k{b}^k\}$

$($a$)$ Order these sets, in terms of computation $($being able to be computed$),$ from the easiest to

hardest:

$($Easiest$)$

$($b$)$ Are any of these non$-$computable? $Y$ or $N.$

If "Yes," which one$($s$)?$