What Are the Two Assumptions Behind a Simple Linear Cost

Essay

What are the two assumptions behind a simple linear cost function? Briefly explain the three ways that a linear cost function may behave?
1)Variations in the level of a single activity (the cost driver)explain the variations in the related total costs; and
"2)Cost behavior is approximated by a linear cost function within the relevant range. This means that total cost versus the level of a single activity that is related to that cost is a straight line within the relevant range.
Once linearity is established, there are three possible types of linearity:"