High-low method; regression analysis. (CIMA, adapted) Anna Martinez, the financial manager at the Casa Real restaurant, is checking to see if there is any relationship between newspaper advertising and sales revenues at the restaurant. She obtains the following data for the past 10 months:

Month	Revenues	Advertising Costs
March	$50,000	$2,000
April	70,000	3,000
May	55,000	1,500
June	65,000	3,500
July	55,000	1,000
August	65,000	2,000
September	45,000	1,500
October	80,000	4,000
November	55,000	2,500