A real estate company wants to study the relationship between house sales prices and some important predictors of sales prices. Based on data from recently sold homes in the space, the following variables are used in a multiple regression model. y x sales price (in thousands of dollars) total floor area (in square feet) x number of bedrooms x distance to nearest high school (in miles) The estimated model is as follows. y=143+0.079x, +15x-4x3 Answer the questions below for the interpretation of the coefficient of x, in this model. (a) Holding the other variables fixed, what is the average change in sales price for each 100-square-foot increase in floor area? dollars (b) Is this change an increase or a decrease? O increase O decrease X