A transistor has a power rating of 8 W for a case temperature of 25°C. If derating factor is 30 mW/°C, the power rating for 55°C, case temperature is-A-8 WB-7.5 WC-7.1 WD-6.8 W-C-7.1 W

C 7.1 W Power rating = 8 (55 25)(30 x 10 3) = 7.1 W.