QBUS6820 Practice Final Exam Semester 1, 2023
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Practice Final Exam
Semester 1, 2023
1. (10 points) Formulate a linear programming model for
x(mi)n |c⊤x| + d⊤x
s.t. ∥x∥∞ + 2∥x∥1 ≤ b.
2. (10 points) Formulate the dual linear program of the following model:
min
x s.t.
6x1 − 6x2 − 3x4
−5x1 + 7x2 − 7x3 − 2x4 =
2x1 − x2 − 4x3 + 2x4 =
7x1 − 5x2 + 4x3 + 4x4 =
−6x1 − 4x2 − 2x3 + 6x4 ≤
x1 ≥ 0, x2 free, x3 ≤ 0, x4 free.
1
−4
4
−3
3. (10 points) Suppose that your optimization model has a variable y which is equal to the product of two variables y = xz, where x is continuous and z is integer. Furthermore, you have the following bounds on x and z:
−10 ≤ x ≤ 10
−2 ≤ z ≤ 4.
Note that since z is integer, this implies that z can only take on values −2, −1, 0, 1, 2, 3, 4. Formulate linear constraints which capture the relationship y = xz .
Hint: introduce binary variables wi ∈ {0, 1} which indicate whether z = i or not. Then z = 对i(4)= −2 i · wi .
4. (20 points) Suppose as many as 10 flights per day can travel between any two of the cities 1, 2 and 3. Set up a maximum flow model that can be used to determine the maximum number of flights in the next three days from city 1 to city 3.
Hint: Let τ denote the end of day τ, so τ = 0 is the start of the first day. You should have a node (i,τ) that represents city i at time τ, for τ = 0, 1, 2, 3. You should also have a source s and a sink t. What are the arcs and capacities between these nodes?
5. (20 points) The Lotus Point Condo Project will contain up to 10,000 dwelling units. Each unit is either a house or an apartment. The project must contain a recreation project: either a swimming–tennis complex or a sailboat marina, but not both.
If a marina is built, then the number of houses in the project must be at least triple the number of apartments in the project. A marina will cost $1.2 million, and a swimming–tennis complex will cost $2.8 million. The developers believe that each apartment will sell for $48,000, and each house will sell for $46,000. Each house or apartment costs $40,000 to build.
Formulate an IP to help Lotus Point maximize profits.
2023-06-05