Nil Rate Band

Relevant part of Qn [Specimen paper]- On 14 August 2005, Opal had made a gift of £100,000 to her daughter, and on 7 November 2014, she made a gift of £220,000 to her son. Both these figures are after deducting all available exemptions.
The nil rate band for the tax year 2005/06 is £275,000.

Required-
(b) Advise Opal Elder as to why the inheritance tax payable in respect of her estate would alter if she were to
live for another seven years until 20 March 2022, and by how much.
Note: You should assume that both the value of Opal Elder’s estate and the nil rate band will remain
unchanged.

Answer acc. to specimen paper-
(b) (1) If Opal were to live for another seven years, then the potentially exempt transfer on 7 November 2014 would become exempt. 1
(2) The inheritance tax payable in respect of her estate would therefore decrease by £88,000 (220,000 at 40%).

My problem- There is no mention that because the PET will be exempt, it will free up more NRB which can then be used on her estate on death. Kindly advise if this is or isn`t the case