The following data is for the small, recently independent island nation of Hibiscus:

Tax rate: 10% flat tax on all citizens since its independence in 2010

Labor supply: 200 workers in 2010, and has grown by 3 percent each successive year
Inflation rate: Has fluctuated between 2 percent and 3 percent annually since 2010
Unemployment rate: A constant 4.5 percent each year since 2010
Exchange rate: Since 2010 has fluctuated by more than 20 percent, both up and down, relative to the rates of major currencies
Interest rate: Has risen from 2.5 percent to 3.5 percent since 2010
Explain why macroeconomists would find it difficult to test the following hypotheses for Hibiscus:
a. Tax rates affect the supply of labor
b. The inflation rate affects the unemployment rate
c. The exchange rate affects the interest rate