Suppose the owner of a convenience store has tracked the average price of a gallon of milk for the months between July 2013 and June 2015. The data are shown in the table.

Month Price ($) Month Price ($) Month Price ($)

7/13 2.247 3/14 2.344 11/14 2.637 8/13 2.108 4/14 2.642 12/14 2.289 9/13 2.111 5/14 2.532 1/15 2.357 10/13 2.352 6/14 2.375 2/15 2.628 11/13 2.374 7/14 2.592 3/15 2.626 12/13 2.192 8/14 2.774 4/15 2.903 1/14 1.989 9/14 3.031 5/15 3.417 2/14 2.130 10/14 2.943 6/15 3.301

a. Produce a time-series plot of the average prices of milk. Identify any time-series components that exist in the data.

b. Identify the recurrence period of the time series.

Determine the seasonal index for each month in the recurrence period.

c. Fit a linear trend model to the deseasonalized data.

d. Provide a seasonally adjusted forecast using the linear trend model for July 2015 and July 2019.