The data file usmacro contains quarterly observations on the U.S. unemployment rate \((U)\), the U.S. GDP growth rate (G), and the U.S. inflation rate (INF) from 1948Q1 to 2016Q1. Plot these series and perform unit root tests on them to assess whether or not they are stationary. In your answer, justify your choice of a test equation, present the results from estimating that equation, state the null and alternative hypotheses, and draw a conclusion. Use a 5\% significance level. What are the orders of integration of the three series?