17. Consider the following time series data. t 1 2 3 4 5 Y 6 11 9 14 15 a. Construct a time series plot. What type of pattern exists in the data? b. Develop the linear trend equation for this time series. C. What is the forecast for t = 6? 18. Refer to the time series in exercise 17. Suppose the values of the time series for the next two time periods are 13 in period 6 and 10 in period 7. a. Construct a time series plot for the updated time series. What type of pattern exists in the data? b. Develop the quadratic trend equation for the updated time series. C. Use the quadratic trend equation developed in part (b) to compute the forecast for t = 8. d. Use the linear trend equation developed in exercise 17 to compute the forecast for t = 8. Comment on the difference between the linear trend forecast and the quadratic trend forecast and what needs to be done as new time series data become available.