An inductor is connected across a capacitor whose capacitance can be varied by turning a knob. We wish to make the frequency of oscillation of this LC circuit vary linearly with the angle of rotation of the knob, going from 2 x 105 to 4 x 105 Hz as the knob turns through 180°. If L = 1.0mH, plot the required capacitance C as a function of the angle of rotation of the knob.