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 3 $ 1,800

February 6 $ 2,300

March 4 $ 1,700

April 5 $ 2,000

May 7 $ 2,300

June 8 $ 2,700

July 2 $ 1,200

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