8.55%. If the rating of the debentures or the issuer is downgraded below AA- by any rating agency, the coupon rate will be increased by 0.25% for each notch of downgrade. If the rating is upgraded, the coupon rate will be decreased by 0.25% for each notch of upgrade until it is restored to AA-. If the rating falls to A or below, the coupon rate will be increased by 0.50% for each notch. If the rating is upgraded, the coupon rate will be decreased by 0.5% for each notch of upgrade until it is restored to A+.