php, 168 bytes

Result

AC

Duration

597ms

Code [DL]

<?php
for($x=[];$i<4;$i++)$x=array_merge($x,fgetcsv(STDIN,9," "));for($i=0;$i<9;)$a+=($i>5)*($x[$i]-=$x[$i+3])*($x[3-~$i%3]*$x[$t=~-$i%3]-$x[++$i%3]*$x[$t+3]);echo$a/6;

stdin

08 74 59
20 58 84
09 09 35
58 46 11

stdout

21393

stderr

PHP Notice:  Undefined variable: i in /volume/CODE on line 2
PHP Notice:  Undefined variable: i in /volume/CODE on line 2
PHP Notice:  Undefined offset: -1 in /volume/CODE on line 2
PHP Notice:  Undefined variable: a in /volume/CODE on line 2

strace