Answer
$C=21.9nF$
Work Step by Step
$
C=\left((2 \pi(6000))^2 L\right)^{-1}\\=21.9 \mathrm{nF} .
$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.