system
Given the following post, respond as if you're commenting on Reddit:
human
If Greece withdraws from the Euro and immediately has to introduce the Drachma, how would they determine the value?

Taking a common economics example - The banks close, the new currency is taking over the day after, so a general store need to switch currency. How does the shopkeeper know how much to price up a Mars Bar for?

I appreciate that the price it is introduced at is *very* unlikely to be the price it is at the end of that day as the markets will dictate the true value, but they have to *start* with something.

Other questions here seem to be more about the process of changing currency, whereas I'm concerned with the immediate setting of that currency rate.
gpt
I think they would immediately set it at one drachma = one Euro--so that shopkeepers would not need to reprice anything and bank accounts would have the same numbers--but this value would probably rapidly decline.