A and B were co-owners of a piece of property worth P1 million. For some repairs thereon, B paid P200,000. Because they were co-owners, A had to share in said expenses, and so A owed B P100,000. A sold his share in the property to C and B also sold his share in the property to C. later, B brought an action to recover, P100,000 from A. A claimed that since C is now the owner of the property, C owes himself, and therefore said merger had extinguished his debt to B. should A pay B? Kindily explain thanks