What is the philosophy of utilitarianism? 

What is the philosophy of utilitarianism?  Provide a concise, complete, and accurate description of the Utility Model of ethical decision-making (“The Utility Model is an ethical decision-making model that asserts a decision or action is ethical if . . .”).  In other words, under this decision-making model what determines whether an action or proposed action or consequence is ethical or unethical? What is its 6-step process/framework? Why is this model a valid way to decide whether an action or situation is ethical or unethical?