Which of the following is not a required element for a legally enforceable contract?

Faber Motors manufactures three lines of cars: high-end security cars for government agencies, commercial cars for consumers and individuals, and professional racing cars

The high-end security cars are sold directly to government buyers by the company. The consumer cars are sold through dedicated dealers who only sell Faber's lines at their outlets. For its professional racing cars, Faber collaborates with Radium Tires, an innovative and renowned tire manufacturer. Faber provides the engine and body, while Radium provides the tires and its expertise on the racing industry. Which term best describes Faber's channel arrangements? A) direct distribution system B) horizontal marketing system C) corporate vertical franchise system D) multichannel distribution system E) administered vertical marketing system

Explain the parol evidence rule

What will be an ideal response?