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 variables-units shipped, weight shipped, or sales value of units shipped-has the closest relationship with shipping expenses. The following information is available: Weight Month Units Shipped Shipped (bs) Sales Value of Shipping Units Shipped Expenses May 10,000 7,500 June 12,000 8,760 $350,000 $38,000 432,000 42,000 July 15.000 9,200 420,000 50,100 August 20,000 10,500 400,000 72,500 September 12.000 October 8,000 7,600 6,000 300,000 41,000 320.000 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. Complete the r-squared values between each possible independent variable and shipping expenses Round answers to two decimal places. Units shipped 0.94 Weight shipped 078 023