E$-$M:$4-28$ Determining cost behavior Identify each cost below as variable $($V$),$ fixed $($F$),$ or mixed $($M$),$ relative to units sold. Explain your reason. Units Sold

$25$ a$.$ Total phone cost

b$.$ Materials cost per unit c$.$ Manager$$s salary

d$.$ Depreciation cost per unit e$.$ Total utility cost

f$.$ Total cost of goods sold

$ $15035$

$3,00060$

$4003,125$