Circuit flow of current
I'm a little rusty with Norton \$ \to \$ Thevenin conversion, so folks feel welcome in pointing out any errors.



We take the encircled portions as norton circuits and convert them to their corresponding thevenin counterparts as below:



With a little straightening of connections and lumping the 3 and 4 ohm resistors followed by applying KCl at the nodes of the current source:





The rest is, I hope, easy to infer from the simplified circuit.