The following is known as the Ackermann function.

function Ack$($m$,$ n is in $\{0,1,2,3,...\})$

if

m $=0$

then

return

n $+1$

else

if

n $=0$

then

return Ack$($m $1,1)$

else

return Ack$($m $1,$ Ack$($m$,$ n $1))$

Compute the values returned by the following function calls.

$($a$)$ Ack$(0,6)=$

$($b$)$ Ack$(1,0)=$

$($c$)$ Ack$(1,1)=$

$($d$)$ Ack$(2,1)=$