$\backslash$table$[[$Week$,$Units,Total Etching$],[1,4,$Cost$],[2,3,18],[3,8,17],[4,6,25],[5,7,20],[6,2,24],[,30,16]]$

For planning purposes, management wants to know the variable etching cost per unit and the total fixed etching cost per week.

Required:

$2-$a$.$ Using the least$-$squares regression method, estimate the variable etching cost per unit and the total fixed etching cost per week.

$2-$b$.$ Express these estimates in the form $Y=a+bx.$

$3.$ If the company processes five units next week, what would be the expected total etching cost?