A company has recorded data on the weekly sales for its product (y), the unit price of the competitor's product (x1), and advertising expenditures (x2). The data resulting from a random sample of 7 weeks follows. Use Excel's Regression Tool to answer the following questions (data set also provided in accompanying MS Excel file).

Weekly sales data
Week	Price	Advertising	Sales
1	0.33	5	20
2	0.25	2	14
3	0.44	7	22
4	0.4	9	21
5	0.35	4	16
6	0.39	8	19
7	0.29	9	15

a. What is the estimated regression equation? Show the regression output.
b. Determine whether the model is significant overall. Use α = 0.10.
c. Determine if competitor’s price and advertising is individually significantly related to sales. Use α = 0.10.
d. Based on your answer to part (c), drop any insignificant independent variable(s) and re-estimate the model. What is the new estimated regression equation? 
e. Interpret the slope coefficient(s) of the model from part (d).