d-dmd, 190 bytes

Result

WA

Duration

533ms

Code [DL]

import std.stdio;void main(){int[30]a;for(i;readf(" %d",&a[i]);)a[i]-=a[i%3]*(i++>2);printf("%d\n",(a[3]*(a[7]*a[11]-a[8]*a[10])+a[4]*(a[8]*a[9]-a[11]*a[6])+a[5]*(a[10]*a[6]-a[7]*a[9]))/6);}

stdin

96 06 98
09 06 71
13 44 71
86 56 54

stdout

stderr

/volume/CODE.d(1): Error: undefined identifier `i`
/volume/CODE.d(1): Error: undefined identifier `i`
/volume/CODE.d(1): Error: undefined identifier `i`
/volume/CODE.d(1): Error: undefined identifier `i`
/volume/CODE.d(1): Error: undefined identifier `i`
Failed: ["/usr/bin/dmd", "-v", "-o-", "/volume/CODE.d", "-I/volume"]

strace