A resource is something used by the actors. A resource may be acquired, maintained, used, possibly made and sold, and disposed of.
Using these simple criteria, the following items become good candidates for problem domain classes:
Key to ask here is, would the users recognize these objects? Would the flower shop use all these objects even if you never wrote any software?
Click the Quiz link below to take a short multiple-choice quiz on the problem analysis phase of the project life cycle.
Domain Classes - Quiz