9.9. Other equilibria in the Barro-Gordon model. Consider the situation described in Problem 9.8. Find the parameter values (if any) for which each of the follow- ing is an equilibrium:

(a) One-period punishment. equals if -1 = 1 and equals b/a other- wise; = each period. =

(b) Severe punishment. (Abreu, 1988, and Rogoff, 1987.) equals if -1 = 1, equals >b/a if 1 and -1, and equals b/a otherwise; Teach period.

(c) Repeated discretionary equilibrium. ==b/a each period.