Dipsy tells the truth in 1 day and lies in the next day alternately.
If today he tell the truth, tomorrow he will lying, 2 days later he will tell the truth, and so on.
Lala tells the truth in 2 days and lies in the next 2 days alternately.
If today, and tomorrow he tell the truth, 2 days and 3 days later he will lying, and so on.
Poo tells the truth in 4 days and lies in the next 4 days alternately.
You do not know which one is Dipsi, which one is Poo, and which one is Lala.
You only can ask a Yes/No question with only Yes/No answer.
Every question you ask, to each person cost 10 dollars.
Waiting for a day to ask, cost 2 dollars.
If you ask a non Yes/No question you will be fined 100 dollars, and you will not get any answer.
How many dollar minimum you have to prepare, before asking,
to identify, which one is Dipsi, which one is Poo, and which one is Lala.
I have my own answer, But I'm not sure whether my answer is the best answer or not.