Per the FARs, define what a contract is, and explain the elements of a contract. Additionally, what is the difference

Per the FARs, define what a contract is, and explain the elements of a contract. Additionally, what is the difference between “Common Law” and “Administrative Law”? Finally, why do we have a contract negotiation process?A few helpful links:https://myclassroom.apus.edu/content/enforced/44588-467154/Week_2_Intro_To_Contracting.doc?_