Lulu's sales in 20X3 are £115 399. The following year, 20X4, sales increase by 4.3%. In 20X5 sales are 7.8% higher than they were in 20X3. Gross profit margin in each of the three years is;

20X3; 19.3%

20X4; 21.4%

20X5; 18.7%

Calculate cost of sales for each of the three years, 20X3, 20X4 and 20X5 (working to the nearest £).