Selecting a Basis for Predicting Shipping Expenses (Requires Computer Spreadsheet*) Penn Company assembles and sells computer boards in western Pennsylvania. In an effort to improve the planning and control of shipping expenses, management is trying to determine which of three variablesunits shipped, weight shipped, or sales value of units shippedhas the closest relationship with shipping expenses. The following information is available: Month units shipped weight shipped Sales value of units shipped shipping expenses May . . . . . . . . . . . . . . . . . . . . . . 3,000 6,200 $100,000 $ 5,600 June . . . . . . . . . . . . . . . . . . . . . 5,000 8,000 110,000 7,700 July . . . . . . . . . . . . . . . . . . . . . . 4,000 8,100 80,000 6,500 August . . . . . . . . . . . . . . . . . . . . 7,000 10,000 114,000 10,400 September . . . . . . . . . . . . . . . . 6,000 7,000 140,000 8,600 October . . . . . . . . . . . . . . . . . . . 4,500 8,000 160,000 8,200 Required a. With the aid of a spreadsheet program, determine whether units shipped, weight shipped, or sales value of units shipped has the closest relationship with shipping expenses. b. Using the independent variable that appears to have the closest relationship to shipping expenses, develop a cost-estimating equation for total monthly shipping expenses. c. U se the equation developed in requirement (b) to predict total shipping expenses in a month when 5,000 units, weighing 7,000 lbs., with a total sales value of $114,000 are shipped.