clear details please, im having a hard time solving this

Save & Exit Submit Help Curtis invests $550,000 in a city of Athens bond that pays 7.75 percent interest. Alternatively. Curtis could have invested the $550,000 in a bond recently issued by Initech, Inc. that pays 10 percent interest with similar risk as the city of Athens bond. Assume that Curtis's marginal tax rate is 24 percent. What is Curtis's after-tax rate of return on the city of Athens bond