Buatlah dialog tentang asking for certainty and uncertainty

Certainty
Sita: Will Edo come here on time?
Dian: Yes, I`m sure.
Sita: How do you sure?
Dian: She is never late before.

Uncertainty
Ms Lela: Why don`t we buy flowers for our class?
Nita: Oh, I think so. It is expensive.
Ms Lela: You are right, but we can collect money.
Nita: I doubt it. I`m broke now. I dont think can get enough money.