Globex Investment Capital Corporation owns six companies that have the following estimated returns (in millions of dollars) if sold in one of the next 3 years:

Company Year Sold (estimated returns, $1,000,000s)

1 2 3

1) $14 $18 $23

2) 9 11 15

3) 18 23 27

4) 16 21 25

5)12 16 22

6) 21 23 28

To generate operating funds, the company must sell at least $20 million worth of assets in year 1, $25 million in year 2, and $35 million in year 3. Globex wants to develop a plan for selling these companies during the next 3 years to maximize return. Formulate an integer programming model for this problem and solve it by using the computer.