When Sandra started transitioning her in$-$store retail sales to an online format, she anticipated a significant shipping expense to go

along with her cost of goods sold. The first year of the transition was rough, though, as she found her shipping costs to be through the

roof, particularly given her fairly steady level of sales throughout the primary $8-$month selling period. Sandra gathered the following

data points for number of units shipped and total shipping costs for the past $8$ months as follows, in an effort to figure out if there was

any rhyme or reason to these costs.

$($a$)$ Use the high$-$low method to determine an estimated cost function for Sandra's shipping costs. Write your final model in $Y=m(x)+b$

format. $($Round variable cost per unit to $2$ decimal places, e$.$g$.15\mathrm{.}25.)$

$Y=$$

$x+$$