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