Gday all, can anyone help with how to calculate the cost base of...

Gday all, can anyone help with how to calculate the cost base of OXR which I receive from conversion from ZFX?

Eg: I have 200 ZFX share, after impliment date 1 July (pls correct me if wrong), it get converted to 639 OXR share.

What CGT event occur? I have a look on ATO but not really understand.
http://law.ato.gov.au/atolaw/view.htm?docid=CLR/CR200844/NAT/ATO/00001

How to calculate my cost base per OXR share? incl broker fee?
How scrip to scrip roll over actually work? I have no idea am I making a gain or loss from ZFX to OXR now. Please help. THank you.