Zoe’s husband had died on 25 July 2007, and 20% of his inheritance tax nil rate band of £300,000 for the tax year 2007–08 was not used.

The nil rate band for the tax year 2009–10 is £312,000, and for the tax year 2010–11 it is £325,000.

Required:
What amount of unused Nil Rate Band will be available to Zoe on her death?