Now, normally I wouldn't like to ask for help, but this is really bugging me, and I'm surely missing some fundamental idea. (Plus, I'm not really sure about the hw help policy on this board, though just looking through a few threads I did notice there were some appeals for help.)

Is this simply a matter of a really long loop rule and junction rules? I thought otherwise because it said it could easily be solved using only mental calculations. So maybe there is a concept I should know?What are the (a) magnitude and (b) direction (up - type "1" or down - type "0") of current i in the figure below, where all resistances are 6.5 Ω and all batteries are ideal and have an emf of 10.0 V? (Hint:This can be answered using only mental calculation.)

Thanks in advance.