In an area with many suburban communities, telephone listings are usually grouped into several different books.23 Patrons in each community i = 1,

c, n are covered in exactly one directory k = 1,

c, m. Numbers of patrons pi are known for each community, as well as (one-way) calling traffic levels ti,j between communities. Engineers seek to design books that maximize the traffic among patrons sharing a common telephone book without listing more than capacity q patrons in any single directory.

Formulate an INLP model to select an optimal collection of telephone books in terms of the decision variables (i = 1,

c, n, k = 1,

c, m)

xi,k ! e 1 if community i goes in book k 0 otherwise