Suppose that an economy currently has an unemployment rate of 7%, an inflation rate of 4% and an expected inflation rate of 4% as well. Suppose that the slope of the short-run Phillips curve is -1/2 (unemployment is on the horizontal axis and inflation is on the vertical axis) and the expected inflation rate stays at 4%. If a central bank wants to lower unemployment rate to 5%, inflation would have to

(a) be decreased to 0%.

(b) be increased to 6%.

(c) be increased to 8%.

(d) stay put.