A small-scale poultry industry grows broilers, layers, and turkeys, and sells them at a profit of $4, $5, and $6 respectively. The house is divided into three chambers sepa- rated by wooden bars to house the three kinds of birds. The house can accommodate no more than 45 birds. The labor time required for broilers and layers is 3 hours each. The turkeys require 4 hours of labor time. The house can grow a maximum of 20 broiler birds, and a maximum of 100 hours of labor are available. Formulate this prob- lem as an LP model to maximize the total profit.