Problem 1: A contractor, Susan Meyer, has to haul gravel to three building sites. She can
purchase as much as 18 tons at a gravel pit in the north of the city and 14 tons at one in the south.
She needs 10, 5, and 10 tons at sites 1, 2, and 3, respectively. The purchase price per ton at each
gravel pit and the hauling cost per ton are given in the table below.
Susan wishes to determine how much to haul from each pit to each site to minimize the total cost
for purchasing and hauling gravel.