Could someone please tell me if this is the correct method for...

Could someone please tell me if this is the correct method for comparing the two listed stocks ?

If: 1 SSN.AMEX share = 20 SSN.ASX shares
AND: AU$1 = US$0.89
Then: AU$0.017 * 20 * 0.89 = US$0.3026

At the moment (7AM AEST) SSN.AMEX is trading at US$0.28.

Therefore: (28/20)/0.89 = AU$0.0157 (round it up to 1.6cents)

Yesterday the Aussie $ was at US$0.88, this morning it is at US$0.89. Would that be the cause of the discrepancy ?

Or seeing as they are actually two separate entities, can we not directly compare the two ?

Thanks in advance ;)
--Dan