(A) a per diem allowance at a rate not to exceed that established by the Administrator of General Services for travel within the continental United States, and by the President or his designee for travel outside the continental United States;

(B) reimbursement for the actual and necessary expenses of official travel not to exceed an amount established by the Administrator for travel within the continental United States or an amount established by the President or his designee for travel outside the continental United States; or

(C) a combination of payments described in subparagraphs (A) and (B) of this paragraph.

(A) because of an incapacitating illness or injury which is not due to the employees own misconduct is entitled to reimbursement for expenses of transportation to the employees designated post of duty, or home or regular place of business, as the case may be, and to payments pursuant to subsection (a) of this section until that location is reached; or

(B) because of a personal emergency situation (such as serious illness, injury, or death of a member of the employees family, or an emergency situation such as fire, flood, or act of God), may be allowed, with the approval of an appropriate official of the agency concerned, reimbursement for expenses of transportation to the employees designated post of duty, or home or regular place of business, as the case may be, and payments pursuant to subsection (a) of this section until that location is reached.

(A) Under regulations prescribed pursuant to section 5707 of this title, an employee who is described in subsection (a) of this section and who, with the approval of an appropriate official of the agency concerned, interrupts the travel assignment prior to its completion for a reason specified in subparagraph (A) or (B) of paragraph (1) of this subsection, may be allowed (subject to the limitation provided in subparagraph (B) of this paragraph)

(B) The reimbursement which an employee may be allowed pursuant to subparagraph (A) of this paragraph shall be the employees actual costs of transportation to the location where necessary medical services are provided or the emergency exists, and return to assignment from such location, less the costs of transportation which the employee would have incurred had such travel begun and ended at the employees designated post of duty, or home or regular place of business, as the case may be. The payments which an employee may be allowed pursuant to subparagraph (A) of this paragraph shall be based on the additional time (if any) which was required for the employees transportation as a consequence of the transportations having begun and ended at a location on the travel assignment (rather than at the employees designated post of duty, or home or regular place of business, as the case may be).