Final answer:
Without a specific relationship model such as Okun's Law, we cannot accurately calculate the unemployment rate from a GDP gap of 13.5%. The natural rate of unemployment in the U.S. in the early 2000s was about 4.5 to 5.5%, and the actual rate stayed near this range in following years.
Step-by-step explanation:
To estimate the unemployment rate based on a given GDP gap, economists might use Okun's Law, which indicates a relationship between the two. However, Okun's Law is not provided here, and without this or a similar econometric model, we cannot directly calculate the unemployment rate from the GDP gap. Instead, let's reference the historical natural rate of unemployment as well as actual unemployment rates to provide context.
In the early 2000s, estimates by economists put the natural rate of unemployment in the U.S. economy at about 4.5 to 5.5%. This rate represents the level of unemployment resulting from all sources except fluctuations in aggregate demand and is considered sustainable without leading to inflationary pressures. Considering this, and historical unemployment rates which hovered around 5% at the end of 2015 and throughout 2016, and the Congressional Budget Office's estimate of the natural rate at 4.74% for early 2017, we can say that actual unemployment rates fluctuate but tend to remain near the natural rate over time.
Given this context, without a specific formula to apply the GDP gap to the unemployment rate, the exact unemployment rate corresponding to a 13.5% GDP gap cannot be accurately determined. None of the answer choices A. 6.25%, B. 6.75%, or C. 6.7% can be verified with the information provided.