Two identical long conducting wires AOB and COD are placed at right angle to each other, with one above other such that $'O'$ is their common point for the two. The wires carry $I_1$ and $I_2$ currents, respectively. Point 'I' is lying at distance 'd' from '$O$' along a direction perpendicular to the plane containing the wires. The magnetic field at the point 'P' will be :

Question

( A ) $\frac{\mu_0}{2 \pi d} (I_1^2 + I_2^2)^{1/2}$
( B ) $\frac{\mu_0}{2 \pi d} (\frac{I_1}{I_2})$
( C ) $\frac{\mu_0}{2 \pi d} (I_1 + I_2)$
( D ) $\frac{\mu_0}{2 \pi d} (I_1^2 - I_2^2)$