An electric bulb of 500 W at 100 V is used in a circuit having a 200 V supply. Calculate the resistance $R$ to be connected in series with the bulb so that the power delivered by the bulb is 500 W.
(1) $30\,\Omega$
(2) $5\,\Omega$
(3) $20\,\Omega$
(4) $10\,\Omega$