13. What contract elements are generally necessary? 14. How are offers terminated? 15. Contracts entered into in cyberspace 16. The "mirror image rule," in Common law and UCC 17. The offeror controls all the terms of a contract. Why? 18. When will a mistake make a contract voidable? 19. Some are "unilateral mistake," what is the other and why does it matter which it is? 20. True or false, mistakes about the value of a contract do not affect the enforceability because value is variable