I am trying to figure out exactly what the question is asking, and how find the proper answer.

Question 3 6 pts Identify the nature of the following costs (i.e., fixed, variable, stepped, mixed, etc.) based on their behavior, and define how they would be influenced by changes in volume of production on both an "in total" and "per unit" basis. Units Sold 20 $36 $80 $1,800 40 $18 $100 $3,600 60 $12 $120 $5,400 80 $9 100 $7.20 b. Rental cost per unit of merchandise sold Total phone expense Total cost of goods sold $140 $160 $7,200 $9,000