33 10  Intangible assets a  cquired software $ Cost Balance at 1 July 2007 451,624 Additions 12,571 Balance at 30 June 2008 464,195 Additions 2,400 Retirement (316,170) Balance at 30 June 2009 150,425 a  ccumulated amortisation Balance at 1 July 2007 415,855 Amortisation expense 28,909 Balance at 30 June 2008 444,764 Amortisation expense 11,930 Retirement (316,170) Balance at 30 June 2009 140,524 Carrying amounts At 1 July 2007 35,769 At 30 June 2008 19,431 At 30 June 2009 9,901