When three identical bulbs of $60\, W$,$200\, V$ rating are connected in series to a $200\, V$ supply,the power drawn by them will be ................ $W$.

$n$ identical bulbs,each designed to consume power $P$ at a certain voltage source,are connected in series across the same source. The total power consumed by them is:

Heating coils rated at $220\, V$ are available with resistances of $55\,\Omega$,$110\,\Omega$,$220\,\Omega$,and $440\,\Omega$. Which resistance value will produce the maximum power?

$4$ bulbs marked $40\, W, 250\, V$ are connected in series with a $250\, V$ mains. The total power consumed is ............. $W$.

$A$ given quantity of water is boiled by an electric heater in $5 \text{ min}$. If the supply voltage of the heater is reduced to half,then the time taken to boil the same quantity of water will be . . . . . . $\text{min}$. (Assume the resistance of the heater remains constant.)

An electric lamp is marked $60\, W$, $230\, V$. The cost of $1\, kWh$ of power is Rs. $1.25$. The cost of using this lamp for $8$ hours is Rs. ................