Except as provided in [Section 6.3(c)(2)], the named fiduciary must render a decision no later than 60 days after receiving the written request for review, unless circumstances make it impossible to do so; but in no event shall the decision be rendered later than 120 days after the request for review is received. If the named fiduciary determines that an extension of time for processing is required, written notice of the extension shall be furnished to the claimant by the plan administrator prior to the termination of the initial 60-day period. The extension notice shall indicate the special circumstances requiring an extension of time and the date by which the plan expects to render the determination on review.