4. A. Use the inequality from Part 3 of Question 3 - to obtain an inequality required for * = 1 to remain stable against DD invaders when CD players take over the whole population. Also draw the ROC diagram for visually representing this stability inequality.

B. Use a diagram similar to that shown in Part A to derive a prediction of what will happen to the CD players' equilibrium probability of cooperating - if the fear and greed payoff differences decrease relative to the cooperation payoff differences.

C. Again use a diagram similar to Part A to derive a prediction of what will happen to the CD players' equilibrium probability of cooperating - if they use cell phones rather than talking face-to-face.

D. What kind of factors could further enhance or degrade the effectiveness of face-to-face communication, and if so, how would this affect the probability of cooperating ?