Mark Price, the new productions manager for Speakers and Company, needs to find out which variable most affects the demand for their line of stereo speakers. He is uncertain whether the unit price of the product or the effects of increased marketing are the main drivers in sales and wants to use regression analysis to figure out which factor drives more demand for its particular market. Pertinent information was collected by an extensive marketing project that lasted over the past 12 years and was reduced to the data that follow:

YEAR	UNIT SALES (THOUSANDS)	PRICE $/UNIT	ADVERTISING ($000)
1	375	279	616
2	675	220	830
3	875	217	1,106
4	1,296	206	1,403
5	1,148	220	1,204
6	1,175	194	1,296
7	875	221	874
8	1,106	203	1,106
9	972	226	695
10	1,239	217	874
11	874	221	695
12	805	248	695

a. Perform a regression analysis based on these data using Excel. (Negative values should be indicated by a minus sign. Round your answers to 4 decimal places.)

c. Predict average yearly speaker sales for Speakers and Company based on the regression results if the price was $275 per unit and the amount spent on advertising (in thousands) was $875. (Enter your answer in thousands. Round your intermediate calculations and final answer to 2 decimal places.)

y bar = Forecasted sales thousand units