Two infinitely long straight conductors lie along x-axis and y-axis in the plane of the page. If they carry current I each along $+x$-axis and $+y$-axis respectively, the net magnetic field at a point with position vector $\vec{r} = $3\hat{i} + 4\hat{j}$\text{ m}$ will be : (A) $\frac{\mu_0 I}{6\pi}\hat{k}$ (B) $-\frac{\mu_0 I}{12\pi}\hat{k}$ (C) $-\frac{\mu_0 I}{24\pi}\hat{k}$ (D) $\frac{\mu_0 I}{48\pi}\hat{k}$