Archer Company is a wholesaler of custom-built air-conditioning units for commercial buildings. It gathered the following monthly data relating to units shipped and total shipping expense:

Month	Units Shipped	Total Shipping Expense
January	2	$	2,200
February	5	$	2,700
March	3	$	2,100
April	4	$	2,400
May	6	$	2,700
June	7	$	3,700
July	1	$	1,600

Using the high-low method, estimate the cost formula for shipping expense.

Variable shipping expense: (per unit)

Fixed shipping expense: (per month)