3. The following data relates to units shipped and total shipping expense for the Adams Company. Units shipped Month January February March April May June July Total Shipping Expense $1,300 $1,600 $1,400 $1,500 $1,700 $1,800 $1,200 ON Using the high-low method, provide the following. SHOW WORK. a. Variable cost per unit b. Total fixed costs C. The cost formula for shipping expense