A Zener diode of power ration \( 1.6 \, \text{W} \) is to be used as voltage regulator. If the Zener diode has a breakdown of \( 8 \, \text{V} \) and it has to regulate voltage fluctuating between \( 3 \, \text{V} \) and \( 10 \, \text{V} \). The value of resistance \( R_8 \) for safe operation of diode will be:
