5.4. LINEAR PROGRAMMING MODELS 77
total cost for producing manually is $7/toaster; semiautomatically is $8/toaster; and robotically is
$8.50/toaster.
(a) Formulate the problem of producing 1000 toasters at minimum cost meeting the resource
requirements. Clearly dene your variables, ob jective and constraints.
(b) Our union contract states that the amount of skilled labor time used is at least 10% of
the total labor (unskilled plus skilled) time used. Update your formulation in (a) to handle this
requirement.
(c) Any unused assembly
oor time can be rented out at a prot of $0.50/minute. Update your
formulation to include this possibility.
Answers to Exercise 61:
(a) Let x1 be the number of toasters produced manual ly, x2 be the number produced semiautomatical
ly, and x3 be the number produced robotical ly.
The objective is to Minimize 7x1 + 8x2 + 8:5x3. The constraints are:
x1 + x2 + x3 = 1000 (produce enough toasters)
x1 + 4x2 + 8x3 4500 (skil led labor used less than or equal to amount available).
40x1 + 30x2 + 20x3 36000 (unskil led labor constraint)
3x1 + 2x2 + 4x3 2700 (assembly time constraint)
x1 0; x2 0; x3 0 (nonnegativity of production)
(b) Add a constraint x1 + 4x2 + 8x3 :1(41x1 + 34x2 + 28x3)
(c) Add a variable sa to represent the assembly time slack. Add +0:5sa to the objective. Change
the assembly time constraint to
3x1 + 2x2 + 4x3 + sa = 2700 (assembly time constraint)
sa 0