Given the following C code and assuming all necessary preprocessor statements and libraries are included.

$1.$char $*$str$1$;

$2.$char $*$str$2$;$$

$3.$char $*$str$3$;$$

$4.$str$1=$ malloc$($sizeof$($char$)*10)$;

$5.$str$2=$ malloc$($sizeof$($char$)*10)$; $$

$6.$if$($str$1!=$ NULL$)$

$7.$ strcpy$($str$1,$ "Holidays"$)$;

$8.$if$($str$2!=$ NULL$)$

$9.$ strcpy$($str$2,$ "Final Exam"$)$;

$10.$ if$($str$3!=$ NULL$)$

$11.$ strcpy$($str$3,$ "Programming"$)$; $$

$12.$ str$3=$ str$1$;$$

$13.$ str$2=$ str$3$;$$

$14.$ str$1=$ str$2$;$$

$15.$ free$($str$1)$;

$16.$ free$($str$2)$;

$17.$ free$($str$3)$;

Check the following line numbers of where a memory management error can potentially occur.