Given the following code:

static void showOutput$($int mark$)\{$

if $($mark $==0)\{$

System.out.print$("*")$;

$\}$

else $\{$

System.out.println$("[")$;

showOutput$($mark $-1)$;

System.out.print$(",")$;

showOutput$($mark $-1)$;

System.out.println$("]")$;

$\}$

$\}$

Can you determine what is produced by the following subroutine calls:

showOutput$(0),$ showOutput$(1),$ showOutput$(2),$ and showOutput$(3)?$

a$.$

showOutput$(0)$ outputs: $*$

showOutput$(1)$ outputs: $[*,*]$

showOutput$(2)$ outputs: $[[*,*],[*,*]]$

showOutput$(3)$ outputs: $[[[*,*],[*,*]],[[*,*],[*,*]]]$

b$.$

showOutput$(0)$ outputs: $[$

showOutput$(1)$ outputs: $*,*$

showOutput$(2)$ outputs: $[[],[]]$

showOutput$(3)$ outputs: $[[[*,*],[*,*]],[[*,*],[*,*]]]$