Tthe end of its manufacturing process, a square silicon wafer (k = 87.8 w/m-k, ρ = 2,330 kg/m, cp = 819 j/kg-k) of width w = 120 mm and thickness t 1 mm, is at an initial temperature of t 325°c and is allowed to cool in quiescent, ambient air at 25°c (v 32.15 x 10 m'/s, a 46.8 x 10 m/s, k 0.0372 w/m-k, b 0.00223 k for air at the film temperature 175°c). a) (10 points) if only the top surface is exposed determine the time required to cool the wafer to a temperature of 50°c b) (10 points) next, a stream of air (at 25°c) flowing at 10 m/s is used to cool the same wafer from part (a). how long (in seconds) wl it take now to cool the wafer to 50°c? c (20 points) an integrated circuit (100 mm square) is fabricated out of this wafer an array of 25 copper fins with a square cross-section (k 400 w/mk, l 20 mm, w 8 mm) is soldered on the top surface of the chip without any contact resistance. this setup is cooled by exposing the top surface to air at 25c with a convective heat transfer coefficient of 50 w/m k. if the integrated circuit is at a uniform temperature of 75 c, determine the power dissipated at steady-state assume that the fins have an adiabatic tip.