Agrocery store wants to examine the relationship between the sales amounts each day at two different locations, store a and store b. the sales amount each day, in dollars, was recorded for 10 days at each store. the least-squares regression line is yˆ=−3,000+1.2x y ^ = − 3 ,000 + 1.2 x , where x x represents the sales amounts each day at store a and y y represents the sales amounts each day at store b. if the mean of the 10 sales amounts for store b is $45,000, what is the mean of the 10 sales amounts for store a?