Dodge It Company's total monthly shipping costs fluctuate with the volume of units shipped. Data from the last six months is as follows:

Month	# of Units	Total Shipping Cost
January	16,300	$31,280
February	16,700	33,360
March	18,900	37,250
April	17,200	34,100
May	21,500	40,900
June	20,900	41,000

Required:

1. Determine the variable cost per unit and the total monthly fixed cost using the high-low method. (5 marks)
2. State the cost formula for the shipping cost. (2 marks)
3. Is it appropriate to use the cost formula created in part 2 for an activity level of 19,000 units? Explain. (2 marks)
4. Describe the behaviour of a variable cost when the level of activity decreases. Provide one example of a variable cost. (2 marks)