For this problem, draw a snapshot of the stack configuration taken just after the execution of line

$6$

$,$

$$two snapshots taken at the end of execution of incBy

$()$

$$function

$($

just before returning from the first and second calls

$)$

$$and finally another snapshot just after the execution of line

$9$

$.$

$($

Hence

$,$

$$in total, you should draw

$4$

$$stack configurations