I came across this question:
Air is flowing with a speed $0.4 \ \text{m/s}$ in the direction of the vector $(−1, −1, 1)$. Calculate the volume of air flowing per second through the loop which consists of straight lines joining, in turn, the following points: $(1,1,0), (1,0,0), (0,0,0), (0,1,1), (1,1,1)$ and $(1,1,0)$.
the loop obviously doesn't lie in a plane, so how do we calculate the flux? and is there a proper way of defining the vector area of such loop?