The water engineer of a city’s municipal department plans to build a surface water reservoir to address the increasing water demand of the city’s fast growing population. The available land for the tank (excluding access land), is 600 ft2. The planned depth of the tank is 10 ft, and it is desired that its length is at least twice its width. Land limitations dictate that the width cannot exceed 20 ft. The tank will be built with reinforced concrete of 1 ft thickness. The city seeks to reduce the total cost of the concrete construction. The cost of 1m3 of concrete construction, which includes not only concrete material costs but also formwork and other related costs, is $150.

a) Using table 9.2 in section 9.0.2(g), classify this problem.

UNSURE: Classification: Linear Integer Programming

b) Using the appropriate decision variables, indicate the water engineer’s objective function and the constraints.

   Decision Variables: Width (W) and Length (L)

       Let W be the width of the tank

       Let L be the length of the tank

   Objective Function: Z =

   Constraints:

c) Solve the problem using a manual plot on a two-dimensional graph.

d) Solve the problem using GAMS or other appropriate optimization software package.