Let the bargaining function F(ut.zt) be given by: F(ut,zt)= (zt)0 (ut) where 8 and are constants. Find an expression for the natural unemployment rate of this economy: a. utn = 1/1+m b. utn = A/1+m c. utn = (A/1+m) d. utn = [(1+m)(zt)0]1/ e. None of the above