8.28%. If the credit rating of the debentures is downgraded to AA, the coupon rate will be increased by 0.5%. If the credit rating of the debentures is downgraded below AA, the coupon rate will be increased 0.25% for each notch of rating downgrade. If the credit rating of the debentures is upgraded to AA, the coupon rate will be decreased by 0.5%. If the credit rating of the debentures is upgraded, the coupon rate will be increased 0.25% for each notch of rating downgrade till AA+.