(a) In the circuit of Fig. P1.1 let vS 5 25 V, R1 5 2 kV, R2 5 3 kV, R3 5 1 kV, and iS 5 4 mA. Find the voltage across and the current through the diode. (b) Repeat, but with vS 5 10 V and iS 5 10 mA....

(a) In the circuit of Fig. P1.1 let vS 5 25 V, R1 5 2 kV, R2 5 3 kV, R3 5 1 kV, and iS 5 4 mA. Find the voltage across and the current through the diode. (b) Repeat, but with vS 5 10 V and iS 5 10 mA. (c) Repeat, but with vS 5 5 V and iS 5 3 mA. (d) Repeat parts (a) through (c), but with a fourth resistance R4 5 1.8 kV connected in parallel with the diode. List the cases in which this additional resistance make a difference, and those in which it doesn’t.