An inductor of 10 mH is connected to a 20 V battery through a resistor of $10\mathrm{~k}\Omega$ and a switch. After a long time, when maximum current is set up in the circuit, the current is switched off. The current in the circuit after $1\mu\mathrm{s}$ is $\frac{x}{100}\mathrm{~mA}$. Then $x$ is equal to \_\_\_\_. (Take $e^{-1} = 0.37$)