On your birthday your great aunt gave you $18000 .
You would like to invest at least $5500 of the money in municipal bonds yielding 5% and no more than $4000 in treasury bills yielding 8% .
How much should be placed in each investment in order to maximize the interest earned in one year?
Assume simple interest applies. let x represent the amount of money in municipal bonds and y represent the amount of money in treasury bills.