A plate with 1 m2 surface area has a surface temperature of 70 0C. The plate is in ambient air with a heat convection coefficient of 13.2 W/m2K and a temperature of 20 0C. In order to increase the heat loss from this plate by a factor of 3, how many pieces of aluminum circular needle fins with a diameter of 2 cm and a length of 10 cm with a heat transfer coefficient of 204 W/m-K should be placed on the surface of the plate? (Only two needle fins are shown in the figure as representative). 

3)