The heat sink of Problem 7.29 is considered for an application in which the power dissipation is only 70 W, and the engineer proposes to use air at T∞ = 20°C for cooling. If the base temperature Tb, must remain below 70°C, what air velocity is required? Properties of the air may be approximated as k = 0.027 W/m ∙ K. v = 16.4 x 10-6 m2/s, and Pr = 0.706. Hint: An iterative solution is required. One approach is to assume the fin efficiency is unity to initiate the iterations.