ruby, 79 bytes

Result

AC

Duration

558ms

Code [DL]

require'matrix'
x=$<.map{|l|Vector[*l.split.map(&:to_i),1]}
p -Matrix[*x].det/6

stdin

74 10 11
61 10 10
67 79 91
26 97 08

stdout

15078

stderr

strace