Step 1 :Define the variables: Let the number of newspaper ads be denoted as x, the number of radio ads as y, and the number of TV ads as z.
Step 2 :Set up the objective function: The function to be maximized is the total exposure, which is given by \(2000x + 1600y + 15000z\).
Step 3 :Set up the constraints: The constraints are given by the budget and the maximum number of ads that can be run per month. These are: \(400x + 200y + 1600z \leq 12000\) (budget constraint), \(x \leq 30\) (maximum number of newspaper ads), \(y \leq 40\) (maximum number of radio ads), and \(z \leq 7\) (maximum number of TV ads).
Step 4 :Solve the linear programming problem: Using these constraints and the objective function, we can solve the problem to find the optimal number of each type of ad to run.
Step 5 :Interpret the solution: The solution to the problem indicates that the store should place approximately \(\boxed{0}\) newspaper ads to maximize exposure.