Ted decides to remodel the family kitchen and signs a contract with Marshall to complete the work. The contract calls for $50$ percent payment upfront and $50$ percent payment upon satisfactory completion of the work. Ted pays Marshall $50$ percent and Marshall completes $100$ percent percent of the work. Despite that fact that Marshall completed all the work, Ted never pays the remaining money owed to Marshall. This breach of contract falls under what area of law?

a$.$ procedural law

b$.$ appellate law

c$.$ discovery rules

d$.$ substantive law