31.28. An L-R-C series circuit is constructed using a 175-22 resistor, a 12.5-F capacitor, and an 8.00-mH inductor, all con- nected across an ac source having a variable frequency and a voltage amplitude of 25.0 V. (a) At what angular frequency will the impedance be smallest, and what is the impedance at this fre- quency? (b) At the angular frequency in part (a), what is the maxi- mum current through the inductor? (c) At the angular frequency in part (a), find the potential difference across the ac source, the resistor, the capacitor, and the inductor at the instant that the cur- rent is equal to one-half its greatest positive value. (d) In part (c), how are the potential differences across the resistor, inductor, and capacitor related to the potential difference across the ac source?