Variable cost and step- variable cost.

Describe the difference between a variable cost and step- variable cost. When s it reasonable to treat step-variable costs as if they were variable cost? Q. 9 What are the advantages of the scatterplot method over the high-low method? The high-low method over the scatterplot method? Q. 11 What is meant by the best-fitting line? Is the best fitting line necessarily a good -fitting line? Explain.