Construct a mathematical model in the form of a linear programming problem. Then solve the problem using the big M method.

An advertising company wants to attract new customers by placing a total of at most 10 ads in 3 newspapers. Each ad in the Sentinel costs $200 and will be read by 2,000 people. Each ad in the Journal costs $200 and will be read by 500 people. Each ad in the Tribune costs $100 and will be read by 1,500 people. The company wants at least 16,000 people to read its ads. How many ads should it place in each paper in order to minimize the advertising costs? What is the minimum cost?