Answer
(e) 500W
Work Step by Step
Let's first calculate resistance of heater
We have
$ P = \frac{V_{rms}^2}{R} = \frac{V_0^2} {2R}$
$\implies R = \frac{V_0^2} {2P} = \frac{(120)^2}{2*1000} \Omega = 7.2\Omega$
When two such heaters are connected in series, total resistance will be
$ R_{eq} = 7.2\Omega + 7.2 \Omega = 14.4 \Omega$
Total power used by these two heaters is given as
$ P = \frac{V_0^2}{2R_{eq}} = \frac{(120)^2}{2* 14.4} W =500W$
