A light source has a small filament at the centre of a spherical glass bulb of radius cm $5$ and negligible thickness. If this source emits $100$ Watts of power in the form of spherical electromagnetic waves, the s m r $..$ electric field E at the surface of the bulb $($in units of Volt$/$m$)$ will be approximately $($a$)1094($b$)4.109($c$)47.15($d$)1547$