Problem $1$

You have been charged with developing quarterly forecasts for overall demand for your company for the

upcoming year. The company has been in business for quite some time, and thus there is a significantly

large data set of historical demand with which to work. You have been instructed by your superiors that

the data set likely contains trend, but company demand is not believed to be particularly seasonal. Also,

the company went through a changeover in management at the end of the second year of the data, with

impacts that are not necessarily known. The demand data are as follows: