The following diagram shows a Zener diode as a voltage regulator. The Zener diode is rated at $$V_{z}=5V$$ and the desired current in load is 5 mA. The unregulated voltage source can supply upto 25 V. Considering the Zener diode can withstand four times of the load current, the value of resistor $$R_{s}$$ (shown in circuit) should be ____ Ω .

A

10

B

4000

C

100

D

1000