$[$Bonus $6$ points$]$ Consider the following program $($the included headers are removed to save space$).$ There are exactly four different possible values at Line A$.$ Fill in the four blanks all the four possible values in the increasing order.

$```$

x $=500$;

pthread$\_$mutex$\_$t lock;

void$*$ increase$($void $*$arg$)\{$

pthread$\_$mutex$\_$lock$($&lock$)$;

x $+=600$;

pthread$\_$mutex$\_$unlock$($&lock$)$;

printf$("\%$d

$",$ x$)$; $//$A $[$

$\}$

main$()\{$

pid$\_$t pid;

pthread$\_$t t$1,$ t$2$;

int y $=700$;

pid $=$ fork$()$;

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

x $*=3$;

y $*=3$;

pthread$\_$create$($&t$1,$ NULL, increase, NULL$)$;

pthread$\_$create$($&t$2,$ NULL, increase, NULL$)$;

pthread$\_$join$($t$1,$ NULL$)$;

pthread$\_$join$($t$2,$ NULL$)$;

return $0$;

$\}$ else $\{$

x $/=2$;

y $/=2$;

pthread$\_$create$($&t$1,$ NULL, increase, NULL$)$;

pthread$\_$create$($&t$2,$ NULL, increase, NULL$)$;

pthread$\_$join$($t$1,$ NULL$)$;

pthread$\_$join$($t$2,$ NULL$)$;

return $0$;

$\}$

$\}$

$```$

Line A: Smallest Possible Value

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Line A: $2$nd Smallest Possible Value type your answer...

Line A: $3$rd Smallest Possible Value type your answer...

Line A: Largest Possible Value

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