crystal, 120 bytes

Result

AC

Duration

1792ms

Code [DL]

Y=`dd`.split;r,t,y,a,b,c,d,e,f,g,h,i=Y.map_with_index{|e,i|e.to_i-Y[i%3].to_i};p (a*e*i+b*f*g+c*d*h-a*h*f-b*i*d-c*g*e)/6

stdin

04 11 69
15 31 77
64 79 87
06 56 05

stdout

6875

stderr

0+1 records in
0+1 records out
36 bytes copied, 0.000193527 s, 186 kB/s

strace