How it's possible to create a valid
Manage Buy Offer in Transaction 5 of the crowdfunding example from the stellar smart contracts reference.
The reference quotes:
Manage Buy Offer: Holding account buys participation tokens at a rate of X per token.
But at the time of presigning I don't know how many participation tokens were sold. So which amount should I put into the buy offer?
With the full amount of participation tokens we get
op_underfunded and without an amount we get