Question $1.[4$ marks$]$

Consider the execution of the following function $($written in the C language$).$

$//$ all the needed headers are included

int$$main$()$

$\{$

$$int$$pid;

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

$$printf$("$A$")$;

$$exit$(0)$;

$\}$

$$printf$("$B$")$;

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

$$printf$("$C$")$;

$$exit$(0)$;

$\}$

$$printf$("$D$")$;

$$waitpid$($pid$,$NULL$,0)$;

printf$("$E$")$;

$$

$$exit$(0)$;

$\}$

$1($a$)$ Draw the process graph for the concurrent program.

In a process graph, each function, including main$(),$ fork$(),$ printf$(),$ waitpid$(),$ and exit$(),$ is represented by a vertex. For each vertex, please write the function name below the vertex, and for printf$()$ write the output character above the vertex. Assume calling printf$()$ will immediately display the content on the screen. Each edge must be directed, with the direction representing the happen$-$before relationship.