An LCR series circuit of capacitance 62 . 5nF and resistance of 50Ω...

Given here, $f = 2kHz = 2000Hz, C = 62 . 5nF = 62 . 5 \times {10}^{- 9}F\text{and}R = 50Ω$

Resonance frequency (amplitude of the current will be maximum in this case) is given by $f = \dfrac{1}{2\pi\sqrt{LC}}$, here, $L$ is the inductance.

Putting the values,

$2000Hz = \dfrac{1}{2\pi\sqrt{L \times 62 . 5 \times {10}^{- 9}}}$

$L = \dfrac{1}{4{\pi}^{2} \times {2000}^{2} \times 62 . 5 \times {10}^{- 9}} = 0 . 1H = 100mH$