A wholesaler of custom-built air-conditioning units for commercial buildings gathered the following monthly data relating to units shipped and total shipping expense: Month January February March April May June July Unita shipped 2 5 3 4 6 7 1 Total shipping expense $2,000 $2,500 $1,900 $2,200 $2,500 $3,060 $1,400 Using the high-low method estimate the cost formula for shipping expenses, calculate the variable shipping expense as well as fixed shipping expense per unit. (All answers are whole numbers -- unless specified otherwise. You should NOT include the $ sign or a comma. E.g. you should type 1000 for one thousand. Negative numbers should be added with a minus sign. c.g. -1000 for a decrease or loss of one thousand.) Variable shipping expense - $ per unit. Fixed shipping expense - $ per unit