intuit inc. develops and sells software products for the personal finance market, including popular titles such as Quicken and turbo tax. Classify each of the following costs and expenses for the company as either variable or fixed to the number of units produced and sold: a. shipping expenses b. property taxes on general offices c. straight-line depreciation of computer equipment d. salaries of human resources personnel e. president's salary f. advertising g. sales commissions h. Cd's i. packaging costs j. salaries of software developers k. wages of telephone order assistants l. user's guides