Intuit Inc. (INTU) develops and sells software products for the personal finance market, including popular titles such as Quicken® 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. Advertising

b. CDs

c. Commissions for online sales personnel

d. Cost of registering each unit sold

e. Hourly wages of help desk employees

f. Packaging costs

g. Salaries of human resources personnel

h. Salaries of software developers

i. Salary of Chief Financial Officer

j. Shipping expenses

k. Straight-line depreciation on equipment

l. Writing of user's guides?