1. The problem statement, all variables and given/known data 2. Relevant equations For the 1st part Ohms law and resistance across zener is 10V I cant get 2nd 3. The attempt at a solution For 1st part I took Vi/p = 18V Putting KVL for left loop of source-->collector-->base-->zener-->ground 18 = Vcb + 10 So Vcb = 8V And Vbe = 0.7V So Vce = 8.7V Correct answer. For second question, P dissipated in transistor = Vce times total current = Vce times Ie Ie = 10 - 0.7 divided by 1 K =9.3mA So P dissipated by transistor = 8.7 times 9.3 = 80.91 mW Book answer is A. Where am I wrong?