A circuit has resistors R 1 = 468 Ω and R 2 = 125 Ω R1=468 Ω and R2=125 Ω , and two batteries V 1 = 12.0 V and V 2 = 3.00 V V1=12.0 V and V2=3.00 V . The variable resistor R is adjusted until the galvanometer reads 0 A 0 A . Calculate the unknown resistance R R .