Answer
$L=0.689\mu H$
Work Step by Step
We know that;
$f=\frac{1}{2\pi\sqrt{LC}}$
This can be rearranged as follows to make $L$ the subject of the formula:
$L=(\frac{1}{C})(\frac{1}{2\pi f})^2$
We plug in the known values to obtain:
$L=(\frac{1}{340\times 10^{-6}})(\frac{1}{2\times 3.1416\times 10400})^2=0.689\times 10^{-6}=0.689\mu H$
