3- Fluctuation, Inc., recorded the following profit figures in 2008-2010. Net sales 2010 $30,500 2009 2008 $25,600 $22,900 Costs and expenses: Cost of products sold $12,600 $10,300 $ 8,350 Selling 7,875 5,025 4,580 General 2,950 2,325 2,150 Research and development 4,100 3,190 2,840 $27,525 $20,840 $17,920 Operating income Other income (expense) Earnings before tax Income tax $ 2,975 $ 4,760 525 $ 3,500 1,480 (300) $ 4,460 1,990 $ 4,980 (400) $ 4,580 2,100 Net income $ 2,020 $ 2,470 $ 2,480 Required: a. Compute the net profit margin for 2008-2010. b. Compute the gross profit margin for 2008-2010. c. Describe the trend in profitability and pinpoint its causes