An ideal 12 V battery (no internal resistance) has its positive terminal connected to junction A and its negative terminal to junction C. Two branches join A to C: branch 1 runs A → B → C with 2.0 Ω between A and B and 4.0 Ω between B and C; branch 2 runs A → D → C with 4.0 Ω between A and D and 2.0 Ω between D and C. A 2.0 Ω resistor is connected directly between junctions B and D. What is the current in the B–D resistor?