$($b$)$ A circuit is shown in Figure $1.$ The diodes are silicon type with a forward$-$biased voltage of $0\mathrm{.}7$ V $.$ With simple block diagram or figure explain the characteristics:

Figure $1$

$($i$)$ Calculate the diode current for $I_{D1}$ and $I_{D2}.$

$($ii$)$ Determine the biasing conditions of diodes D$1$ and D$2.$

$[8$ marks$]$

$($iii$)$ What are the voltages between nodes A and $B?$

$[4$ marks$]$

$($iv$)$ Calculate the voltages at nodes A and B $.$

$[3$ marks$]$

$[4$ marks$]$