Problem 2 Use the high-low method to develop a cost function for shipping expense based on the data below. Then estimate shipping costs for a month when nine units are shipped. Month January February March April May June July Units Shipped 3 6 4 5 7 8 2 Total Shipping Expense $1,800 $2,300 $1,700 $2,000 $2,300 $2,700 $1,200