TOPIC: Need clarification on Sequence Activities" Process

Hi,

I purchased the PMPrepcast material and it is very good for learning and preparing for the exam. I am going through the "Sequence Activities" process and I have a question on the example of the lag activity (selling cheese). You have mentioned that it is a finish-to-finish reletionship. Why it cannot be a finish-to-start activity? Cheese cannot be sold until is made, correct? Please help me understanding.

Thanks,
Balaji.