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 variable - units shipped, weight shipped, or sales volume of units shipped - has the closest relationship with shipping expenses. The following information is available:

Month	Units Shipped	Weight Shipped (lbs)	Sales Value of Units Shipped	Shipping Expense
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 the spreadsheet program, determine whether units shipped, weight shipped, or sales value of units shipped has the closest relationship with shipping expense.

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 5,000 units, weighing 7,000 pounds, with a total sales value of $114,000 are shipped.