## Network Simplex Problem

Hi guys,

I am confused about the network simplex method.
Here are the graphics what I did so far:
http://files.ivovorrath.de/network.jpg
http://files.ivovorrath.de/network2.jpg

I sketched the network and the spanning tree in green, which is my BFS. Then I calculated the y's and finally the row zero coefficients for the NBV's (all are less than zero).
My problem is that I do not know if a NBV is lower or upper. In case of the maximum flow of 12, all NBV's are in between upper and lower limits. Are they then upper or lower NBV's, when I test if they are less or greater than zero?

I hope someone has an answer, because I am really desperate.

IV