ruby, 106 bytes

Result

WA

Duration

541ms

Code [DL]

require'matrix'
a,b,c,d=STDIN.read.lines.map{|l|Vector[*l.split.map{|i|i.to_i}]}
p Matrix[b-a,c-a,d-a].det

stdin

89 07 79
97 90 85
32 79 08
34 66 70

stdout

313446

stderr

strace