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 45°. The value of C is:

a) 1/πf(2πfL+R)
b) 1/πf(2πfL−R)
c) 1/2πf(2πfL+R)
d) 1/2πf(2πfL−R)