Regression, effect on sales per capita

The data in the file attached contains information on your firm’s sales per capita, advertising expenditure per capita, and average local income. Regress sales per capita on advertising expenditure per capita, controlling for local income as an interval variable, where intervals are <$35,000, $35,000–$44,999, $45,000–$54,999, and $55,000+, and <$35,000 is the base group. For the remainder of the question, assume the data-generating process is SalesperCapitai = α + β1AdExpperCapitai + β2Inc35-45i + β3Inc45-55i + β4Inc55i + Ui and that all other necessary assumptions toward establishing causality and performing inference hold.

1. Interpret the coefficients for the income intervals from your regression.
2. According to this regression, what is the effect on sales per capita when average local income increases from $35,000−$44,999 to $55,000+