An investment advisor is advising a wealthy client. The client would like to invest USD 500,000 in a bond rated at least AA. The advisor is considering bonds issued by Company X, Company Y, and Company Z, and wants to choose a bond that satisfies the client's rating requirement, but also has the highest yield to maturity. The advisor has gathered the following information:

Company/Bond	X	Y	Z
Bond rating	AA+	A+	AAA
Annual coupon rate (%)	3.50	3.56	3.38
Time to maturity in years	5	5	5
Price (USD)	975	973	989
Par value (USD)	1,000	1,000	1,000

Assuming semi-annual coupon payments, which bond should the investment advisor purchase for the client?