$6\mathrm{.}2$ For a given product, the past three years' demand per month is presented in the following table:

$\backslash$table$[[$Month$,1,2,3,4,5,6,7,8,9,10,11,12],[$Year $1,203,198,210,234,186,175,214,194,200,180,195,300],[$Year $2,224,232,241,262,189,180,225,220,240,192,237,314],[$Year $3,243,239,251,260,194,192,240,236,253,200,249,327]]$

$($a$)$ Use linear regression to predict total demand in year.

$($b$)$ Find forecasted demand for every month of year $4$ using seasonal analysis.

$($c$)$ Find forecasted demand for every three months $($quarter$)$ of year $4$ using seasonal analysis. Graphically show the past demand$-$versus$-$forecasted values.