Find the general flow pattern of the network.

Question

20<---A
|\B__>x(4)
|/
80<---C
I believe the system of equations for A,B,&C is-A: x(1)+x(3)=20 B: x(2)=x(3)+x(4) C: 0=x(1)+x(2)
Assuming flows are all nonnegative, what is the largest possible value for x(3). Sorry, this would be a lot easier if I could post a picture. But I got to the answers x(1)=20-x(3) x(2)=x(3)-100 x(4)=-100 x(3) is free. I'm not sure what to do from here.