Ann: Highest Grade Spodumene Intersections Ever Drilled in the NT-CXO.AX, page-124

Pretty sure this same question was covered last week. To convert your options into ordinary shares it will cost 5c per option, hence the cost base of your converted ordinary shares for recognising a capital gains event (at the point of sale) becomes 5c+cost of options. If you have multiple option purchases and have traded options along the way, each distinct tranche of unsold options must be used when determining cost base.
For example:
I bought 300k options at 1c
Then a further 200k at 2c
And a final 50k at 4.5c
On the way up I sold 200k options at 4c.
I decide to convert the rest of my options.
The cost base is hence 5c+1c = 6c for 100k ordinary shares (the first 300k options minus the 200k that I sold)
5c+2c = 7c for the next 200k ordinary shares
5c+4.5c = 9.5c for the final 50k ordinary shares