7. The frequency of the sinusoidal voltage source in the circuit below is adjusted until ???? and ???? are in-phase. a. What is the value of ????? b. If ???? ൌ 15 cosሺ????????ሻ V (where ???? is the frequency found (a)), what is the steady-state expression for ????? (Hint: ???? and ???? are in-phase when the impedance to the right of the 1 ???????? resistor is purely resistive.)