A power supply has an open-circuit voltage of 40.0 V and an internal resistance of 2.00 Ω. It is used to charge two storage batteries connected in series, each having an emf of 6.00 V and internal resistance of 0.300 Ω. If the charging current is to be 4.00 A,
(a) What additional resistance should be added in series?
(b) At what rate does the internal energy increase in the supply, in the batteries, and in the added series resistance?
(c) At what rate does the chemical energy increase in the batteries?