What Is the Significance and Function of Phonological Rules in Language?

What is the significance/function of phonological rules in language? Illustrate your answer with reference to three such rules (in English or any language you are familiar with), and give examples of how each rule operates. (968 words)
INTRODUCTION
Phonological rules are a system of writing, using formal notation, which allows linguists to express how to pronounce speech phonetically. Phonological rules are part of every speaker's linguistic competence (Finch 2000, p. 64). As well, these rules operate unconsciously (Finch 2000, p. 64). …