Please calculate using excel calculation methods if possible.

A manager recorded the number of gallons of ice cream sold for the past six periods. He asked you to

choose a forecasting model to predict the demand for gallons of ice cream in Period $9.$ You consider

applying a three$-$period simple moving average model, and a three$-$period weighted moving average

model with weights of $0\mathrm{.}4,0\mathrm{.}35$ and $0\mathrm{.}25.$

a$)$ Which model is better for this data set $($hint: show all your work and calculations using measures of

forecast accuracy$)?(9$ points$)$

b$)$ What is the forecast of demand for period $9,$ considering the best model? $(1$ point$)$