Cost behaviour

4.11 The following information for advertising and sales has been established over the past six months: Month Sales revenue Advertising expenditure $'000 $'000 1 155 3 2 125 2.5 3 200 6 4 175 5.5 5 150 4.5 6 225 6.5 Using the high-low method which of the following is the correct equation for linking advertising and sales from the above data? A Sales revenue = 62,500 + (25 × advertising expenditure) B Advertising expenditure = – 2,500 + (0.04 × sales revenue) C Sales revenue = 95,000 + (20 × advertising expenditure) D Advertising expenditure = – 4,750 + (0.05 × sales revenue) Sir I don't understand how to do this question The correct answer is option A I tried substituting the figure 3000(month 1) in advertising expenditure for the option A answer but the answer doesn't seem to come =62500+(25*3000) =137500 This 137500 was not equal to 155000 in month 1 Sir how could the answer be option A when it doesn't even tally according to the formula Sir also i do understand that there is another approach for this question using high low method but i want to know this approach by substituting the data in the equations because I find it more convenient(It doesn't take much time unlike high low )