For question 1, it asks me to find the operating point by different methods. But I have no idea to solve it. Can anyone give some hints for me? I can just think about the diode can be replaced by an ideal diode, a 0.5V dc source and a 0.2/4=0.05Ω resistor. For question 3, I have solved the (a) part Ic=2.33mA. For the (b) part, I have calculated Ib=Ic/β=0.0292mA Ie=Ib+Ic=2.3625mA However, I don't know how to find the value of Rb without Vbe. I have asked the tutor but he said that I do not need to assume Vbe=0.7V in this question. Thanks for reading my questions.