The thermal conductivity of plastics is about 1000 times lower than that for the aluminum. If the…

The thermal conductivity of plastics is about 1000 times
lower than that for the aluminum. If the fin efficiency is 95% for an aluminum
fin of 6 mm height, the height required for a similar (same thickness and cross
section) plastic fin for 95% fin efficiency would be:

(a) 6 mm (b) 0.006 mm (c) 0.2 mm (d) 0.5 mm (e) can’t tell

Hint: Do not calculate the fin efficiency. Assume the heat
transfer coefficient as constant and same.