An inductor of inductance $2 \mu \mathrm{H}$ is connected in series with a resistance, a variable capacitor and an AC source of frequency 7 kHz . The value of capacitance for which maximum current is drawn into the circuit is $\frac{1}{x} F$, where the value of $x$ is $\_\_\_\_$ . (Take $\pi=\frac{22}{7}$ )