$1.2 billion was issued as century bonds, which must be repaid in 100 years. This century bond issuance is the largest century issuance in the higher education sector to date. The Century bond has a coupon rate of 4.45 percent. The other $800 million of the bond issuance were 30-year bonds, with a coupon rate of 3.5 percent. $300 million of the 30-year bonds were green bonds. The proceeds from green bonds can only be used to fund green capital projects that support environmental or climate-related objectives. Among other green projects, the University of Michigan plans to build a geothermal heating and cooling system for one of the buildings on campus. The bonds were issued at par, with the University of Michigan's fiscal year ending on June 30th. What does the term "at par" mean