Please do Not use Excel, I need the formula way. Thank you very much in advance.

l. A fastfood chain decided to carry out an experiment to assess the inuence of advertising expenditure on sales. Different relative changes in advertising expenditure, comparedto the previous year, 1were made in nine regions of the country= and resulting changes in sales levels were observed. The accompanying table shows the results. Increase in Increase Advertising in Sales Expenditure (9'3) ('56) :1. Estimate by least squares the linear regression of increase in sales on increase in advertising expenditure. 1). Find a 95% condence interval for the slope of the population regression line