A circular transistor of $10-mm$ diameter is cooled by impingement of an air jet exiting a $2-mm-$

diameter round nozzle with a velocity of $20\frac{m}{s}$ and a temperature of $15C.$ The jet exit and the

exposed surface of the transistor are separated by a distance of $10mm.$ If the transistor is well

insulated at all but its exposed surface and the surface temperature is not to exceed $85C,$ what is

the transistor's maximum allowable operating power?