Classifying variable and $$xed selling costs Classify each of the following as a variable or $$xed cost with respect to a unit of product that is sold: $($a$)$ Commissions paid to sales personnel $($b$)$ Advertising expenses $($c$)$ Salaries of sta$$ processing orders $($d$)$ Delivery truck depreciation expenses $($e$)$ Protective shipping packaging for each unit of product $($f$)$ Insurance on sales o$$ces $($g$)$ Product shipping costs $($h$)$ Wages paid to order$-$taking sta$($i$)$ Cost of computers used to maintain customer $$les