$(1)$ How is the break$-$even point defined, and which methods can be used to calculate the level of sales in units or dollars? $($LO $5-5)$

$(2)$ What is the purpose of target profit analysis, and which methods can be used to calculate sales level in units or dollars? $($LO $5-6)$

$(3)$ How is the margin of safety defined, and how is it calculated in dollars and as a percentage? $($LO $5-7)$