When a p - n junction is reverse-biased, the current is nearly...

The net current in a $p$-$n$ junction diode is the difference between the diffusion current and the drift current.

$I = I_{\text{diffusion}} - I_{\text{drift}}$

The drift current is due to minority charge carriers and is nearly independent of the applied bias voltage. It is equal to the reverse saturation current.

$I_{\text{drift}} = 25 \mu\text{A}$

When the diode is forward-biased, the net current is given as $75 \mu\text{A}$.

$75 \mu\text{A} = I_{\text{diffusion}} - 25 \mu\text{A}$

$I_{\text{diffusion}} = 75 \mu\text{A} + 25 \mu\text{A} = 100 \mu\text{A}$