(a) Is this a valid model? Explain why or why not.

(b) Is this a good fit? Explain why or why not.

(c) Which predictors have a significant impact on sales from second store onward? Explain why.

(d) According to this model, does the real time message increase the sales from second store onward? Is this impact the same for consumers with different loyalty status? Explain.

Coefficients : Estimate Std. Error t value Pr(>Itl) (Intercept) 19.0284 3.5766 5. 320 1. 06e-07 *** age 0. 6429 0. 1038 6. 192 6. 20e-10 *** genderMale -1. 7635 2. 2691 -0.777 0. 4371 loyalty_status low -15.4805 2. 0079 -7.710 1.39e-14 *** realtime_message1 3.3700 1.9225 1. 753 0. 0797 . Signif. codes : 0 '* * *' 0. 001 ' * *' 0. 01 ' *' 0. 05 '. ' 0. 1 ' ' 1 Residual standard error: 91.15 on 9027 degrees of freedom Multiple R-squared: 0.01248, Adjusted R-squared: 0.01205 F-statistic: 28.53 on 4 and 9027 DF, p-value: