A shoe store developed the following estimated regression equation relating sales to inventory investment and advertising expenditures.

y$=23+12x_1+7x_2$

where

$x_1=$ inventory investment $($$$1,000s)$

$x_2=$ advertising expenditures $($$$1,000s)$

$y=$ sales $($$$1,000s).$

$($a$)$ Predict the sales $($in dollars$)$ resulting from a $$15,000$ investment in inventory and an advertising budget of $$11,000.$

$

$($b$)$ Interpret $b_1$ and $b_2$ in this estimated regression equation.

Sales can be expected to increase by $ $$ for every dollar increase in inventory investment when advertising expenditure is held constant. Sales can be expected to increase by $ for every dollar increase in advertising expenditure when inventory investment is held constant.