Answer if you know the answer only. This is test

Fuel, like diesel and propane, is too heavy for the Mars mission to carry much, if any, of it. So power is likely to be provided by a solar array instead of a generator. The energy collected from the solar arrays will be stored in large battery banks. Most of the circuits will have a load of about 12 Ω. If 4 A is needed to run the equipment, what voltage does the battery bank need to be?​