Zerbel Company, a wholesaler of large, custom-built air conditioner units for commercial buildings, has noticed considerable fluctuations in its shipping expense from month to month, as shown below: Where y= total shipping cost and x= number of units shipped, Zerbel used the high/low method to estimate its shipping expenses as follows: Y=600X+9,000 Y=375X+13,480 Y=389X+15,667 Y=500X+13,000 Y=350X+16,600