SCM $345$: Logistics Management $-$ Data Analysis Project

Richard has been hired by Sun Devil Bookstore as a supply chain planner at the beginning of $2019.$ His first job is to forecast the sales for the first $4$ months in $2019.$ The past two years historical sales data is listed below:

$\backslash$table$[[,$Date,Sales in $$1000$ s$],[2017,$Jan,$27],[$Feb$,29\mathrm{.}5],[$Mar$,38\mathrm{.}1],[$Apr$,43\mathrm{.}6],[$May$,25\mathrm{.}9],[$Jun$,32\mathrm{.}4],[$Jul$,39\mathrm{.}9],[$Aug$,42\mathrm{.}3],[$l$,$Sept,$24\mathrm{.}7],[$Oct$,36\mathrm{.}1],[$Nov$,43\mathrm{.}4],[$Dec$,44\mathrm{.}7],[2018,$Jan,$27\mathrm{.}4],[$Feb$,37\mathrm{.}3],[$Mar$,44\mathrm{.}6],[$Apr$,43\mathrm{.}8],[$May$,31\mathrm{.}2],[$Jun$,39\mathrm{.}7],[$Jul$,46\mathrm{.}7],[$Aug$,48\mathrm{.}1],[$Sep$,32\mathrm{.}1],[$Oct$,40\mathrm{.}7],[$Nov$,46\mathrm{.}6],[$Dec$,47\mathrm{.}7]]$

The supply chain manager has told Richard that the sales performance of the bookstore cycles every four months. Richard also finds a sticky note attached on the wall next to his right hand scribbled "Winter's, $==0\mathrm{.}5",$ which was left by the ex$-$planner that resigned last month. So$,$ Richard first adopted the explanner's approach to forecast the monthly sales of Jan$\mathrm{.}2019-$ Apr. $2019.$