Treasury Spot Rates equivalent, question, selling, payment, figure

glamorous

The yield to maturity on a bond equivalent basis on 6-month and I-year T-bills
are 2.8% and 3.2%, respectively. A 1.5-year, 4% Treasury note is selling at par.

What is the 1.5-month Treasury spot rate?

Ok, in solving this question why do you not use the 1.5-year, 4% Treasury note as the 1.5 month treasury spot rate? This note is used to figure out the coupon payment. Why?