If an employer is subject to COBRA and provides an HRA that permits post-employment expenses against the HRA credits otherwise unused at the time of termination, is the 'loss of coverage' under the HRA for COBRA purposes (a) termination of employment, when the employee no longer accrues new HRA credits, or (b) when the HRA credits are all used up (or some other time post-employment, per the HRA design, when HRA credits can no longer be used)?