If the number of employees who are separated pursuant to subsection (c)(3) is less at any location than the number of excess firemen in freight and commuter service and second and third brakemen in freight service at such location, as determined by the Corporation, the Corporation may, after 210 days after August 13, 1981, designate for separation employees in engine service or train service respectively in inverse order of seniority, beginning with the most junior employee in active service at such location until the excess firemen in freight and commuter service and second and third brakemen in freight service, at that location have been eliminated. An employee designated under this subsection may choose (1) to furlough himself voluntarily, in which case the next most junior employee protected under the fireman manning or crew consist agreements or any other agreement or law, in the same craft or class at such location may be separated instead and receive the separation allowance, or (2) to exercise his seniority to another location, in which case the Corporation may separate, under the provisions of this subsection, the next most junior protected employee in active service at the location to which seniority ultimately is exercised.