Main Street Store, Inc. had net sales of $1,200,000 for the fiscal year ended August 31, 2003. Gross profit for the firm was $350,000 and operating expenses (consisting of selling, general, and administrative expenses) were $311,000. Earnings before taxes (pre-tax income) equals $30,000 and net income was $18,000. Calculate the firms:

a. cost of goods sold

b. operating income

c. interest expense

d. income tax