A proton moves in the positive \(x\) direction at \(4.00 \times 10^{4} \mathrm{~m} / \mathrm{s}\). Calculate the magnitude of the magnetic field at the point \((x, y)=(+2.00 \mathrm{~mm},+1.00 \mathrm{~mm})\) as the proton passes through the origin.