Leave enough current for regulation

A 15 V source feeds a 500 Ω series resistor and a 5 V Zener-regulated output. The Zener needs at least 2 mA to stay in the stated constant-voltage region.

Find the maximum load current that preserves regulation.

Organize the givens & assumptions

Supply: 15 V
Series resistor: 500 Ω
Regulated output: 5 V
Minimum Zener current: 2 mA

The 5 V model holds only for Zener current at least 2 mA. Assume all power limits are satisfied and source/resistor values are fixed.

A $20\ \mathrm{mA}$
B $22\ \mathrm{mA}$
C $2\ \mathrm{mA}$
D $18\ \mathrm{mA}$

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