The processing carrier shall pay, decline to pay, or settle each written claim within 60 days after its receipt by that carrier, except where the claimant and the carrier agree in writing to a specific extension based upon extenuating circumstances. If the carrier declines to pay a claim or makes settlement in an amount different from that sought, the carrier shall notify the claimant in writing of the reason(s) for its action, citing tariff authority or other pertinent information developed as a result of its investigation.