The heater filament of an electric kettle is a conducting wire of length $$L$$ and diameter $$D$$. When connected to a line voltage source, it takes $$6 $$minute to raise the temperature of $$500 ml$$ of water by
$$40°$$C. If the heater filament is replaced by a new one of same material but length $$2L $$ and diameter $$2D$$, the
time taken for heating the same quantity of water through the same temperature difference will be
(Assume that entire system is thermally insulated)