Alright, so i'm drawing a blank with this problem, maybe I've just been staring at it for too long. It is as follows:

The loop current in a series LC circuit with a voltage source satisfies

LI''+(1/C)I=fo*sin(120*pi*t)

If L=10^-3 H and the constant C is measured in F, for which value(s) of C does the circuit exhibit
(a) pure resonance?
(b) the beats phenomenon? In that case, find the slow, beats frequency in terms of C

Thanks in advance for the help.