San Diego Company is wholesaler of air-conditioning units for commercial buildings. It gathered the following monthly data relating to units shipped and total shipping expense: Required: 1. Using the high-low method, estimate a cost formula for total shipping expense in the form Y=a+Bx. 2. If the company forecasts 9 units shipped next month, what would be expected total shipping expense? 3. Compare your high-low estimates with a least-squares regression analysis estimated the total fixed costs to be $700 per month and the variable cost to be $220 per unit (Y=700+220x). 4. What factors, other than the number of units shipped, are likely to affect the company's shipping expense