Using the Least Squares Method of linear regression, calculate the demand forecast for the next four periods $($Periods $19-22)$ using the information shown below. NOTE: Use the provided Y$-$intercept and slope shown below; no need to calculate the actual Y$-$intercept and slope.

$\backslash$table$[[,$Week Number$],[,10,11,12,13,14,15,16,17,18,],[\backslash$table$[[$Cases$],[$Shipped$]],2,500,2,650,2,325,2,200,2,700,2,750,2,900,2,850,2,925,]]$