Match each of the following costs of producing T$-$shirts with the appropriate classification $($a$-$c$).$

a$.$ Variable cost

b$.$ Fixed cost

c$.$ Mixed cost

Ink used for screen printing

Warehouse rent of $$8,000$ per month plus $$0\mathrm{.}50$ per square foot of storage used

Thread

Electricity costs of $$0\mathrm{.}038$ per kilowatt$-$hour

Janitorial costs of $$4,000$ per month

Advertising costs of $$12,000$ per month

Accounting salaries

Color dyes for producing different colors of T$-$shirts

Salary of the production supervisor

Straight$-$line depreciation on sewing machines