Two similar coils are kept mutually perpendicular such that their centers co-inside. At the centre, find the ratio of the mag. field due to one coil and the resultant magnetic field by both coils, if the same current is flown.
(a) $1: \sqrt{2}$
(b) $1: 2$
(c) $2: 1$
(d) $\sqrt{3}: 1$