When did you receive this inheritance? If (for example) the inheritance was taken after 7 April 2009, then you'd pay CAT (not CGT) amounting to 25% of €80,000 less €43,400 (the threshold for gift/inheritances from aunt/uncle to nephew/niece), i.e. €9,150. If it was before then, the rate will be lower and the threshold will be higher so your liability should be less.
Vanilla is correct. So depending on the date of your aunt's death, the applicable CAT rate could be 20%, 22% or 25%. And the applicable threshold amount (i.e. the amount you do not pay tax on) could be €52,121, €54,254 or €43,400.