Reference point was chosen to be at Va. I'm trying to understand the logic behind it. It is clear that Vc = - Vs because if Vc was the reference point at Va the voltage potential between Va and the reference point Vc is Vs. Therefore, Va = Vs, Va - Vc = Vs if Vc is reference. However, when Vc is the reference point, don't we have Vc -Va = -Vs? Va is reference so 0 volts which mean Vc = -Vs. At the Ohm law at IR1. If Va is the reference point which mean it is zero voltage. All the nodes are using it as a reference to ground and to my understand the voltage at the node is based on the higher potential - the lower potential. If that's the case, how can the higher potential be the reference point when it was given a value of zero with respect to all other nodes??