4.8 Figure 4.31 shows the biyearly smoothed (12-month moving average)

number of sunspots from June 1749 to December 1978 with n = 459 points that were taken twice per year. With Example 4.9 as a guide, perform a periodogram analysis of the sunspot data (the data are in the file sunspots.dat) identifying the predominant periods and obtaining confidence intervals for the identified periods. Interpret your findings.