Air Company is a wholesaler of custom-built air conditioning and heating units for commercial buildings. The data below show the number of units shipped and the total shipping expenses for the past whole year.

Month	Units Shipped	Total Shipping Expenses
October, 2021	12	$ 7,300
November, 2021	11	$ 7,000
December, 2021	10	$ 6,600
January, 2022	3	$ 2,900
February, 2022	6	$ 4,600
March, 2022	4	$ 3,400
April, 2022	5	$ 4,000
May, 2022	7	$ 5,000
June, 2022	8	$ 5,400
July, 2022	2	$ 2,400
August, 2022	1	$ 1,200
September, 2022	9	$ 6,000

Required:

Prepare a graph using the above data (use either Microsoft Excel or by hand on paper). Shipping expenses will be on the vertical axis and units shipped will be on the horizontal axis.

Does the relation between shipping expenses and the number of units shipped appear to be linear? Explain your response.

Based on a visual inspection of the graph, do you think shipping expense is a true variable cost or a mixed cost? Explain.