A trust officer at Wildcat Bank

A trust officer at Wildcat Bank needs to determine how to invest $360,000 in the following collection of bonds to maximize the annual return.

BOND                            ANNUAL RETURN       MATURITY          RISK            TAX FREE

A                                               11%                         LONG              HIGH                YES

B                                               9%                          SHORT            LOW                   YES

C                                              9.5%                        LONG              LOW                   NO

D                                             12%                          SHORT             HIGH                YES

E                                              9%                          SHORT            HIGH                  NO

The officer wants to invest at least 55% of the money in short-term issues and no more than 60% in high-risk issues.

Also, due to the local high tax rates, at least 30% of the investment money should at least be $7,500 while the return collected from high-risk options cannot be more than $6,600.

a) formulate and list the linear programming model for this problem.

b) use the software "LINGO" to slove the above model and report the optimal solution.

c) What is the highest annual return from the above optimal solutions?

d) which constrains are binding? why