Calculate the magnetic potential difference $V_\rm m$ for the following paths as shown by the solid lines. 
Dotted lines are only for there for symmetry aspects! 
The wires conduct the following currents:
 $|I_1|=2 ~\rm A$
 
 $|I_2|=5 ~\rm A$
 
 $|I_3|=11 ~\rm A$
 
 $|I_4|=7 ~\rm A$
 
Pay attention to the signs of the currents (given by the diagrams) and of the results!
 
 
 Result 
 
 
 
Based on the right-hand rule and the part of a full revolution the following results:
 Task: $+I_1 - I_2 = -3 ~\rm A$ 
 
 Task: $+{{1}\over{4}} I3 = 11/4 ~\rm A$ (it does not matter which way the path goes from the startpoint to the endpoint, as long as it has the same direction and number of revolutions) 
 
 Task: $-{{1}\over{4}} I1 = -0.5 ~\rm A$ 
 
 Task: $+2 \cdot I_2 - 1 \cdot I_3 = -1 ~\rm A$