The original question:
So far I know it has 4 surfaces and only the bottom face will have -k.
I thought of breaking it down by
S1: Front Face
S2: Left Face with points (0,0,0), (1,0,0), and (0,0,1)
S3: Right Face with Points (0,0,0), (0,1,0) and (0,0,1)
S4: The bottom face