Harriet died on 21 October 2017. Her husband had died previously and his estate on death (including transfers made in the last seven years of his life) had absorbed £1 77,840 of the nil-rate band at that time. Calculate the nil -rate band which is available when calculating the IHT due on Harriet's death, assuming that her husband died in:

(a) May 2006

(b) July 2008.