Maximum Magnetic Field From a Moving Charge

A positive charge $q$ moves with a constant velocity of $\vec{v} = 3.0 \times 10^6\ \mathrm{m/s}$ in the $+y$-direction. The charge is at the origin at time $t=0$. At what time $t$ is the magnitude of the magnetic field at point $P(2.0\ \mathrm{cm}, 0, 0)$ at its maximum?