List the elements required for a valid contract and provide a definition for each element. $(10$ points$)$

Define in your own words bilateral contract and unilateral contract and provide an example for each. When it comes to revoking a contract what is the main difference between a unilateral contract and a bilateral contract? $(10$ points$)$

Define in your own words Quasi Contract providing the elements required and provide an example of a Quasi Contract. $(5$ points$)$

Define Promissory Estoppel providing the elements required and provide an example of when the Court will use Promissory Estoppel. $(5$ points$)$