Classify four cases:
1. 'One of these two distinct phones for Rs 40,000' without identification: uncertain subject.
2. 'This machine for Rs 40,000, provided you also give me a Rs 10,000 loan': extraneous benefit condition.
3. 'Payment when the crop is ready' without a known date: indefinite deadline.
4. Artificial bids to increase price: najsh, with validity a separate question.
These are teaching illustrations, not additions to the source text.