I want to know the answer to the following question:
What river was the Mercian region south of?
All the background I'm provided with is that "In terms of geography the Northumbrian region lay north of the Humber River; the Mercian lay north of the Thames and South of the Humber River; West Saxon lay south and southwest of the Thames; and the smallest, Kentish region lay southeast of the Thames, a small corner of England.". Is that enough to answer the question?
Answer: yes