Selecting a Basis for Predicting Shipping Expenses (Requires Computer Spreadsheet*) Cambridge SoundWorks sell portable speakers systems and bluetooth headphones. 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 (lbs.)	Sales Value of Units Shipped	Shipping Expenses
May	10,000	7,500	$350,000	$38,000
June	12,000	8,760	432,000	42,000
July	15,000	9,200	420,000	50,100
August	20,000	10,500	400,000	72,500
September	12,000	7,600	300,000	41,000
October	8,000	6,000	320,000	35,600

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. Use the equation developed in requirement (b) to predict total shipping expenses in a month when 14,000 units, weighing 9,380 lbs., with a total sales value of $420,000 are shipped.