Luther Industries needs to raise $25 million to fund a new office complex. The company plans on issuing ten-year bonds with a face value of $1000 and a coupon rate of 7.0% (annual payments). The following table summarizes the YTM for similar ten-year corporate bonds of various credit ratin.

YTM: AAA=6.7% AA=6.8% A=7% BBB=7.4% BB=8%

What rating must Luther receive on these bonds if they want the bonds to be issued at par value?