Indicate whether each of the following costs is a product cost or a period cost:
a. Cleaning supplies for the office.
b. Freight on goods purchased for resale.
c. Salary of the marketing director.
d. Freight on goods sold to customer with terms FOB destination.
e. Utilities expense incurred for office building.
f. Advertising expense.
g. Insurance on vans used to deliver goods to customers.
h. Salaries of sales supervisors.
i. Monthly maintenance expense for a copier.
j. Goods purchased for resale.