Macon Vitamins sells a variety of vitamins and herbal supplements to small health food stores. Macon purchases the vitamins and supplements from leading manufacturers. Identify each of the following costs incurred by Macon Vitamins in terms of its cost behavior-variable, fixed, mixed, or step.
a. Vitamin C tablets
b. President's salary
c. Sales commissions ($1.00 per case)
d. Straight line depreciation on office equipment
e. Shipping (billed in 100-pound increments)
f. Advertising
g. Telephone charges (monthly fee of $35 plus long distance charges)