a brain teaser while we await the amex action

Currently with the $AU at parity with the $US, we divide the American share price by 20 to establish what the Australian share price should be.

For ease of calculations lets assume at this moment SSN in the states is trading at $4.00.......meaning the value of SSN's Australian shares would be 20c

Now if the $AU was to fall to 70c US overnight and the American shares were still trading at $4.00 at what price would you expect the Australian shares to be trading at?

Please provide your calculations of how you derived your answer.