(a) Suppose a country imports oil. The world oil price has recently decreased, affecting the country's domestic aggregate supply. Explain how policymakers find the trade-off between unemployment and inflation in the short run in the country. Diagram(s) required.

(b) The natural rate of unemployment is 5% in a given country. The country's central bank mistakenly believes that the rate should be 6% and successively pursues a monetary policy to make it at 6%. Demonstrate how this will affect the economy. Diagram required.