An electronics company is looking to develop a regression model to predict the number of units sold for a special running watch. Data is provided below: (Use excel Data Analysis)

Sales (units)	Price ($)	Advertising ($)
500	100	50
480	120	40
485	110	45
510	103	55
490	108	40
488	109	30
496	106	45

(a) Development the regression model.

(b) Interpret the best model with all relevant information included.

(c) Determine the coefficient of determination and interpret.

(d) Determine the least squares trend line.