(A) Subject to subparagraphs (B) and (C)— (i) the total monthly benefits to which beneficiaries may be entitled under sections 402 and 423 of this title for a month on the basis of the wages and self-employment income of an individual whose primary insurance amount is computed under section 415(a)(2)(B)(i) of this title shall equal the total monthly benefits which were authorized by this section with respect to such individual’s primary insurance amount for the last month of his prior entitlement to disability insurance benefits, increased for this purpose by the general benefit increases and other increases under section 415(i) of this title that would have applied to such total monthly benefits had the individual remained entitled to disability insurance benefits until the month in which he became entitled to old-age insurance benefits or reentitled to disability insurance benefits or died, and (ii) the total monthly benefits to which beneficiaries may be entitled under sections 402 and 423 of this title for a month on the basis of the wages and self-employment income of an individual whose primary insurance amount is computed under section 415(a)(2)(C) of this title shall equal the total monthly benefits which were authorized by this section with respect to such individual’s primary insurance amount for the last month of his prior entitlement to disability insurance benefits.

(B) In any case in which— (i) the total monthly benefits with respect to such individual’s primary insurance amount for the last month of his prior entitlement to disability insurance benefits was computed under paragraph (6), and (ii) the individual’s primary insurance amount is computed under subparagraph (B)(i) or (C) of section 415(a)(2) of this title by reason of the individual’s entitlement to old-age insurance benefits or death, the total monthly benefits shall equal the total monthly benefits that would have been authorized with respect to the primary insurance amount for the last month of his prior entitlement to disability insurance benefits if such total monthly benefits had been computed without regard to paragraph (6).

(C) This paragraph shall apply before the application of paragraph (3)(A), and before the application of subsection (a)(1) of this section as in effect in December 1978.