Consider each of the following independent situations:

Shaniqua Boyer just started her new job as controller for St$.$ Matthias General Hospital. She wants to get a feel for the cost behavior of various departments of the hospital. Shaniqua first looks at the radiology department. She has annual data on total cost and the number of procedures that have been run for the past $15$ years. However, she knows that the department upgraded its equipment substantially $2$ years ago and is doing a wider variety of tests. So$,$ Shaniqua decides to use data for just the past $2$ years.

Francis Hidalgo is a summer intern in the accounting department of a manufacturing firm. His boss assigned him a special project to determine the cost of manufacturing a special order. Francis needs information on variable and fixed overhead, so he gathers monthly data on overhead cost and machine hours for the past $60$ months and enters them into his personal computer. A few keystrokes later, he has information on fixed and variable overhead costs.

Ron Wickstead sighed and studied his computer printout again. The results made no sense to him. He seemed to recall that sometimes it helped to visualize the cost relationships. He reached for some graph paper and a pencil.

Lois March had hoped that she could find information on the actual cost of promoting new products. Unfortunately, she had spent the weekend going through the files and was only able to find data on the total cost of the sales department by month for the past $3$ years. She was also able to figure out the number of new product launches by month for the same time period. Now, she had just $15$ minutes before a staff meeting in which she needed to give the vice president of sales an expected cost of the average new product launch. A light bulb went off in her head, and she reached for paper, pencil, and a calculator.

Required:

Determine which of the following cost separation methods is being used: the high$-$low method, the scattergraph method, or the method of least squares.