A toroid made of $\text{CRGO}$ has an inner diameter of $\text{10 cm}$ and an outer diameter of $\text{14 cm}$. The thickness of the toroid is $\text{2 cm}$. $200$ turns of copper wire is wound on the core $\mu_{o} = 4\pi\times10^{-7}$ $\text{H/m}$ and $\mu_{R}$ of $\text{CRGO}$ is $3000$. When a current of $\text{5 mA}$ flows through the winding, the flux density in the core in millitesla is ______________.