$3)$ Consider a single$-$phase, full$-$wave thyristor rectifier with a resistive load $(10)$ connected to a power grid by means of a transformer. Assume that the magnitude of the grid voltage can vary between $+/-10\%$ around its rated value of $120$Vrms$.$ A$)$ Calculate the minimum voltage $($in rms$)$ at the secondary of the transformer so that the dc voltage across the resistor can be regulated at $100$ V by varying $.$ Hint: The minimum value of should be used when the rms value of the grid voltage is at its minimum. B$)$ What value of should be used when the rms value of the grid voltage is at its maximum so as to regulate the voltage across the load at its rated average value? C$)$ Draw the waveforms of the source voltage and current and load voltage and current for the case described in B$).$