A variable cost is: $(3$ points$)$

a$.$ The cost that depends on the activity level such as direct labor and raw material has been

used.

b$.$ All operating costs that are not raw materials or direct labor.

c$.$ A constant $($relatively$)$ cost regardless of the activity level.

d$.$ The amount of a past transaction, such as asset depreciation, that is recorded as part of

bookkeeping.