How is the payout eligibility age lump sum withdrawal amount computed?

The payout eligibility age (PEA) lump sum withdrawal amount is computed based on 20% of members' Retirement Account (RA) balance* and any CPF LIFE premium balance at members' payout eligibility age. The PEA lump sum withdrawal amount includes the $5,000 that can be withdrawn from age 55.

*Excluding top-ups made under the Retirement Sum Topping-up scheme, CPF LIFE Bonus & Deferment Bonus

Illustration: Member turned age 55 in 2013

As at the day he turns age 65:
Retirement Account balance $107,400 (A)
CPF LIFE premium balance $ 74,000 (B)
Top-ups made under Retirement Sum Topping-Up scheme $ 20,000 (C)
CPF LIFE Bonus $ 2,200 (D)
Payout eligibility age lump sum withdrawal amount computed at age 65 [(A+B-C-D) x 20%] - $5,000 = $ 26,840

Retirement Account balance包括55-65产生的利息吗？
CPF LIFE premium balance是什么？65岁时不是RA所有的钱都拿去做CPF LIFE premium吗？为什么还有Retirement Account balance和CPF LIFE premium balance？