Table 10-1 a Company Has Decided to Use 0-1 Integer Programming to Programming

Table 10-1
A company has decided to use 0-1 integer programming to help make some investment decisions.There are three possible investment alternatives from which to choose,but if it is decided that a particular alternative is to be selected,the entire cost of that alternative will be incurred (i.e. ,it is impossible to build one-half of a factory) .The integer programming model is as follows:
Maximize 5000 X₁ + 7000X₂ + 9000X₃
Subject to: X₁ + X₂ + X₃ ≤ 2 (only 2 may be chosen)
25000X₁ + 32000X₂ + 29000X₃ ≤ 62,000 (budget limit)
16 X₁ + 14 X₂ + 19 X₃ ≤ 36 (resource limitation)
all variables = 0 or 1
where X₁ = 1 if alternative 1 is selected,0 otherwise
X₂ = 1 if alternative 2 is selected,0 otherwise
X₃ = 1 if alternative 3 is selected,0 otherwise
The optimal solution is X₁ = 0,X₂ = 1,X₃ = 1
-According to Table 10-1,which presents an integer programming problem,the optimal solution is to select only two of the alternatives.Suppose you wished to add a constraint that stipulated that alternative 2 could only be selected if alternative 1 is also selected .How would this constraint be written?

A) X₁ = X₂
B) X₁ ≤ X₂
C) X₁ ≥ X₂
D) X₁ + X₂ = 2
E) None of the above