(b) Yes, this is the best statement of the issue. 

It asks the exact question that must be decided to resolve the dispute that has arisen between A and B. 

Note that the issue is expressed in generic terms - 'buyer' and 'seller' and 'goods' rather than 'X' and 'W' and 'coffee beans'.

Analysing the facts properly and stating the issue accurately is an essential prerequisite to finding the relevant law and resolving the dispute.