((a)) Except as provided in subsection (b) or section 1370 of this title, each officer who is retired under section 8321 or 8322 of this title—
((1)) unless otherwise entitled to a higher grade, shall be retired in the grade in which he was serving at the time of retirement; and
((2)) unless otherwise entitled to higher pay, is entitled to retired pay computed under .
((b)) Each officer who is retired while serving in the grade of admiral, vice admiral, general, or lieutenant general by virtue of an appointment under or who is retired while serving in a grade to which he was appointed or promoted under or promoted under section 602 (as in effect before ) or section 5721 of this title—
((1)) unless otherwise entitled to a higher grade, shall be retired in the grade he would hold if he had not received such an appointment; and
((2)) unless otherwise entitled to higher pay, is entitled to retired pay computed under .
((c)) A warrant officer who retires under section 8321, 8322, or 8323 of this title may elect to be placed on the retired list in the highest grade and with the highest retired pay to which he is entitled under any provision of this title.