As a proton passes the origin, its velocity is $3.0\times {10}^5\mathrm{m}/\mathrm{s}$in the positive x direction. What is the magnitude of the magnetic field at the point ($12.0\mathrm{cm}$, $5.0\mathrm{cm}$, $0.0\mathrm{cm}$)?

Identify the relevant formula for the magnetic field due to a moving charge, which is given by the Biot-Savart Law: \( \mathbf{B} = \frac{\mu_0}{4\pi} \frac{q \mathbf{v} \times \mathbf{r}}{r^3} \), where \( \mathbf{B} \) is the magnetic field, \( \mu_0 \) is the permeability of free space, \( q \) is the charge, \( \mathbf{v} \) is the velocity, and \( \mathbf{r} \) is the position vector from the charge to the point of interest.