The unemployment rate for the civilian labor force for selected years is shown in the graph. (Source: U.S. Bureau of Labor Statistics, www.bls.gov) The $x$ -axis represents the number of years since the year 2000 .
a. Over what interval(s) did the unemployment rate increase?
b. Over what interval(s) did the unemployment rate decrease?
c. Estimate the values of any relative maxima or minima on the interval (0,9) .