for 3-3 I did this : first I found the resistance of the resistor since I know that a diode has to always be with a resistor. so R=V/I = .75v/400ma => R=1.875 Now Idiode2= .8v/1.875=.42Amps

For figure 3-22 a and b we have to find the load current and the load voltage: for a I did this:

Idiode=v/r => 19.3/1k=19.3ma

and the load voltage I think it should be 0v

but for circuit b im not sure if it is the same process can someone explain part b to me.