A marketing manger of large savings and loan association that has branches throughout the state would like to mail a promotional piece to prospective borrowers. Manger has selected three regions in which to do a mailing. A marketing agency can supply lists of prospective borrowers in each region, as shown below.

          Region               list size                        cost/ name

            1                      10,000             .11

            2                      20,000             .12

            3                      30,000             .13

 The manger would like to have a pool of 15,000 and would like the mail to contain at least 10 percent of the people on each list. Formulate an LP model that will accomplish these requirements. Assume there is no overlap among lists, and that any quantity can be ordered from each list.