how can I figure out the profit before taxes and the other missing numbers for year 4 with the information given below?

I already figured out the average for the previous years but I am stuck where the blanks are.

Selected income statement items are shown for Astrotech Company. Compute the missing amounts for each of the four years. What basic accounting equation did you apply in making your calculations? (Hint: To estimatethe Year 4 missing numbers, compute the typical percentage each expense item is of sales for Year 1 to 3 and apply the percentage figure for each expense items to Year 4's sales).
	Year 1		Year 2		Year 3		Year 4
Sales	$12,011		$5,984		$11,545		$10,000
Cost of goods sold	3,011		2,992		2,886		2,500
Gross margin	$9,000		$8,976		$8,659		$7,500
Other expenses	$6,201		$6,429		$6,296
Profit before taxes	2,799		509		2,363
Tax Expense	1,120		1,019		945
Net Income	$1,679		$1,528		$1,418