1. The problem statement, all variables and given/known data Calculate the power drawn from the batteries by the amplifier. The batteries are +9v and -9v. The amplifier draws a current of 8mA from each of its power supplies. 2. Relevant equations P = VI 3. The attempt at a solution I'm just a little stumped as to what to do for the current. I know V = 18v but I'm not sure how the 2 currents interact with each other. Do they cancel out? Do they multiply or sum up? I'm sure I can finish the rest if I understand that.