Given the following program, please determine how many times the word "hello" is printed out. Assume that fork$0$ is always successful. $(5$ points$)$ #include #include int main$()\{$ pid t a$,$ b; fork$()$; fork$()$; if $($a $0)$ fork $()$; if $($b $0)$ fork $()$; printf$("$hello

$")$; return $0$;