4) Data from a sample of5 pharmacies are used to examine the relation between prescription sales 1lrolume and the percent of prescription ingredients purchase directly from the suppliers. The sample data are shown here: Sales Volume, y % of Ingredients (in $1,000) Purchased Directly, x xy y x-square 25 10 250 625 100 55 18 9'90 3,025 324 50 25 1,250 2,500 625 3'5 40 3,000 5,625 1,600 110 50 5,500 1,2100 2,500 Total 315 143 10,990 23,375 5,149 a} Find the Least Square Error regression line. b) Interpret the meaning of slope. c) Predict sales volume for a pharmacy that purchase 15% of its prescription ingredients directly from the supplier