Intuit Inc. develops and sells software products for the personal finance market, includin popular titles such as Quickbooks® and TurboTax®. Classify each of the following costs and expenses for this company as either variable or fixed to the number of units produced and sold:

a. Packaging costs
b. Sales commissions
c. Property taxes on general offices
d. Shipping expenses
e. Straight-line depreciation of computer equipment
f. President’s salary
g. Salaries of software developers
h. Salaries of human resources personnel
i. Wages of telephone order assistants
j. CDs
k. Users’ guides