1. The problem statement, all variables and given/known data Air is flowing with a speed of 0.4m/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 (1,1,0), (1,0,0), (0,0,0), (0,1,1), (1,1,1) and (1,1,0). 2. Relevant equations 3. The attempt at a solution So I don't know if this is meant to be a line integral or surface one? My feeling is that it should be a surface integral over that pentagonal surface..I.e. double integral of F.n dS..where F is (-1,-1,1).. Firstly, is this right? Secondly, how do I use the fact that the speed of flow is 0.4? Thirdly, how do I find the normal to the plane?! Finally, how do i integrate over the surface of the pentagon in the double integral?! Thanks!