An electric teakettle has a multiposition switch and two heating coils. When only one of the coils is switched on, the well-insulated kettle brings a full pot of water to a boil over the time interval ∆t. When only the other coil is switched on, it requires a time interval of 2∆t to boil the same amount of water. Find the time interval required to boil the same amount of water if both coils are switched on
(a) In a parallel connection and
(b) In a series connection.