Assume the analysis of Friedman and Phelps is correct, so that the following equation is valid:
Unemployment rate = Natural rate of unemployment − a × (Α ctual inflation − x).

In this equation,
a. a = 0 at the point of intersection of the short-run and long-run Phillips curves.
b. x = 0 when the actual rate of inflation equals the expected rate of inflation.
c. x is the expected rate of inflation.
d. a is a parameter that measures how much actual inflation responds to expected inflation.