Question $3$: $(20$ pts$)$

For the circuit shown below:

If all diodes are the ideal diodes, find the currents running through $R_1,R_2,R_3$ :

$I_{R1}=$

$(10$ pts$)$

If the diodes are pn$-$junction diodes with turn$-$on voltage at $0\mathrm{.}7$ V $,$ employing the "Constant$-$Voltage$-$Drop" model, find the voltages at nodes: A$,$ B$,$ C:

$V_A{V}_B(10$ pts$)$