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 advert effect plot, what is the expected value of sales when advert=3? 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