There are two current planer coils made each from identical wires of length L. $C_1$ is circular coil (radius R) and $C_2$ is square (side a). They are so constructed that they have same frequency of oscillation when they are placed in the same uniform magnetic field B and carry same current. Find a in term of R.

Question

$\begin{array}{1 1} a=3R \\ a=2R \\ 3a=R \\ 2a= R \end{array} $