b$.$ In columns $5,6,$ and $7$ compute the absolute error, the squared error, and the absolute percentage error. Using these results, find the MAD, MSE, and MAPE for the MA$(3)$ forecasts for months $4$ through $24.$

c$.$ Repeat parts $($a$)$ and $($b$)$ for six$-$month moving averages. $($These calculations should appear in columns $8$ through $12.)$ Which method, MA$(3)$ or MA$(6),$ was more accurate for these data?