Data was collected on 100 houses recently sold in a city. It consisted of the sales price (in $), house size (in square feet), the number of bedrooms, and the annual real estate tax (in $).

(The Excel file is attached)

1) Please investigate how the variables are related to one another. You can do this graphically by constructing scatter plots of all pair-wise combinations

2) Please fit a linear model to predict the impact of the most important variables on sales price. 

3) Please then check the if the selected variables have a significant impact of sales price or not (5% significance level)