Compare nature and classes of contracts.

Comparison should examine

• express contract (i.e., written or spoken)
• executory contract (i.e., not fully performed)
• executed contract (i.e., completed by both parties)
• quasi-contract (i.e., some element missing, but enforceable by law)
• sales contract (i.e., sale of property, rent realty, wills, estates, and trusts)
• employment contract (i.e., business organization contract)
• implied contract (i.e., action)
• unilateral contract (i.e., contains one promise)
• bilateral contract (i.e., contains two promises).