Consider a problem where all plants ship to all warehouses, which in turn ship to all retail outlets. Location cities consist of plants: (1) Los Angles, (2) Seattle, (3) Memphis; warehouses: (4) Las Vegas, (5) Pittsburgh; and retail outlets: (6) San Francisco, (7) Chicago, (8) Miami. The supply capacity at plants LA, Seattle, and Memphis are 700,300 , and 500 , respectively, while the demand requirement at retail outlets SF, Chicago, and Miami are 400, 200, and 900 , respectively. The unit shipping cost is $5 from LA to LV, \$15 from LA to Pittsburgh, \$7 from Seattle to LV, \$14 from Seattle to Pittsburgh, $10 from Memphis to LV, \$6 from Memphis to Pittsburgh, \$9 from LV to SF, $8 from LV to Chicago, $16 from LV to Miami, $13 from Pittsburgh to SF, $3 from Pittsburgh to Chicago, and $12 from Pittsburgh to Miami. Formulate an LP model to minimize the total transportation cost. Hint: Define the variables as follows: Let Xij be the quantity shipped from city i to city j (e.g., X25 be the quantity shipped from Seattle to Pittsburgh)