statistics economic

The below is the regression output that explains sales in terms of price and advert. The regression is linear where sales = b1+ b2*price + b3*advert. Use alpha = 0.05, critical t-value = 1.99,n =75 Coefficients: Estimate Std. Error (Intercept) 118.91 6.35 price -7.91 1.10 advert 1.86 0.68 The price effect plot measures how sales change when price changes (advert = mean(advert) = 1.844). The advert effect plot measures how sales change when advert changes (price = mean(price) = 4.830). Based on the price effect plot, what is the slope of the line? price effect plot advert effect plot 85 80 80 78 sales sales 75 76 74 70 5.0 5.5 6.0 6.5 0.5 1.0 1.5 2.0 2.5 3.0