7. Chips Bakery has been having trouble forecasting the demand for its special highfiber bread and would like your assistance. The data for the weekly demand and the autocorrelations of the original data and various differences of the data are shown in Tables P-7A–D.

a. Inspect the autocorrelation plots and suggest a tentative model for these data. How did you decide on this model? (Note: Do not difference more than necessary. Too much differencing is indicated if low lag sample autocorrelations tend to increase in magnitude.)

b. Using a computer program for ARIMA modeling, fit and check your identified model with the bread demand data.

c. Write down the equation for forecasting the demand for high-fiber bread for period 53.

d. Using a computer program for ARIMA modeling, forecast the demand for high-fiber bread for the next four periods from forecast origin 52. Also, construct 95% prediction intervals.