Answers for tutorial 3:

Note: VT = kT/q is assumed to be 26 mV for these answers. Further I_C = I_S exp(V_BE/VT).

1. Min R_B is 7.4 kOhm (accurate), 7.7 kOhm (approx). If beta becomes 200, then for the same R_B, 1.8 V of collector-base forward bias will try to appear. Of course this will not happen and the maximum forward bias will be 0.7 V (V_C will never go below V_E, right?).
2. Min R_1 is 52.3 kOhm, R_2 is 23.6 kOhm. Max voltage at collector is 2.5 V. Min voltage at collector is 0.76 V.
3. R_1 of 35 kOhm, R_2 of 15 kOhm will make sure that the base current is 20x smaller than the current through R_1, R_2. Change in I_C is 5%.
4. Max R_2 is 20.3 kOhm.
5. Base of Q1 is at 1.51 V, emitter of Q1 is at 0.75 V, ICQ of Q1 is 1.58 mA, collector of Q1 is at 2.34 V. Base, collector of Q2 are at 0.75 V, emitter at 0 V, ICQ of Q2 = ICQ of Q1 = 1.58 mA.
6. R_B is 74 kOhm.