2. (10 points) Consider the saltemp time series from the astsa package in R. a. Discuss the frequency behavior visible in the realization and the Parzen spectral density estimate. b. Use the Butterworth filter to perform a low-pass filter with cutoff frequency 0.15. Discuss the effect of the filter on the filtered time series and its associated spectral density. c. Use the Butterworth filter to perform a high-pass filter with cutoff frequency 0.32. Discuss the effect of the filter on the filtered time series and its associated spectral density.