Hello! I need this whole question solved. Thanks!

A shoe store developed the following estimated regression equation relating sales to inventory investment and advertising expenditures. y = 21 + 12x1 + 7X2 where X, = inventory investment ($1,000s) X2 = 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, and b, 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