In the conversation below which verbs are non-finite?
Cook: What shall I cook for dinner tonight, sir?
Master: Prepare some sweets, I am expecting two guests.
Cook: Fine, sir.
Master: Also make some fruit salad.
Cook: Yes, sir.
There are 6 verbs and I'm bit confused. I think that shall and am are finite verbs, and the rest are non-finite, but I don't understand why. I read some material too on the topic but it is of no help.
I want to know what characteristics these verbs have which makes them non-finite.