In a circuit L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45º. The value of C is -

Question

( A ) $\frac{1}{\pi f(2\pi f L+R)}$
( B ) $\frac{1}{\pi f(2\pi f L-R)}$
( C ) $\frac{1}{2\pi f(2\pi f L+R)}$
( D ) $\frac{1}{2\pi f(2\pi f L-R)}$