Consider the following method:

public int xSum$($TreeNode root$)$

$\{$

if root $==$ null$)$

return $0$ ;

return $(($Integer$)$ root.getValue$())-$

xSum$($root$.$getLeft$())+$ xSum$($root$.$getRight$())$;

$\}$

$\}$

What value is returned by xSum $($root$)$ if root points to the following tree? $($Hint: work from the bottom up$.)$

a $,-9$

b $,-10$

C $5$

d $12$

e $20$