The maximum rated power of the LED is 2 mW and it is used in the circuit with input voltage of 5 V as shown in the figure below. The current through resistance $$R_S$$ is 0.5 mA.
The minimum value of the resistance of $$R_S$$, to ensure that the LED is not damaged is _______ k$$\Omega$$.

A

6

B

2

C

4

D

5