The treasury bills are a way for the treasury to raise short term money from the public. The treasury bills are purchased for a price that is less than their par value. When they mature, the government pays the holder the full par value. Your interest is the difference between the purchase price of the security and what you get at maturity. The Treasury bills price nver can be above par (100). The interest actually are apid upfront, so the TB price is the par value minus the actual value of the future interest.
Maturity: usually less than 1 year.
Price: discount par value.
Coupon: No coupon.
Mature at par value.
n= number of days to maturity
r= annualized yield of the treasury bill