If Dodge then accepts $150 from Charles in settlement of the claim, will Dodge succeed in an action against Charles for the remaining $50?
No, because Charles honestly believed that Dodge did not have a legal right against him for the $200. 
No, because Charles was not contractually obligated to pay Dodge $200 in the first plac
Yes, because Arthur's debt of $200 was liquidated and undisputed. 
Yes, because Dodge honestly believed that he had a legal right against Charles for the full $200. 