18 1. Pharma is a business that produces pain medication (in boxes with 200 bottles of medication per box). There are four possible plants, denoted by p P = {1,2,3, 4} that can be used for production (if needed). The annual capacity (in boxes) of each plant is given by ap. The produced pain medication can be shipped (in boxes) through one of six warehouses, denoted by we W = {1,2...,6}, with a maximum capacity of mu (in boxes per warehouse). The cost (in R/bottle) of producing pain medication at each plant is given by up. The distance (in km) between plant p and warehouse w is given by dp and it costs the company R5 to transport one box of medication for one kilometer. Pharma has ten customers, denoted by c C = {1, 2,..., 10}. The distance (in km) between warehouse w to customer c is given by Dwe. Each customer's annual demand (in bottles) is denoted by ne. If a plant or a warehouse is used to produce or store medication, a fixed annual cost of operating that plant or warehouse is incurred. The fixed cost of operating plant p and the fixed cost of operating warehouse w are given by fp and Fu respectively. Formulate a Pure Integer Linear Program (PILP) to help Pharma determine which plants and warehouses to use in order to minimise the total facility, production and transportation cost of satisfying the annual demand for pain medication.