S20-3 Using the high-low method Paul owns a machine shop. In reviewing the shop's utility bills for the past 12 months, he found that the highest bill of $3,500 occurred in July when the machines worked 1,500 machine hours. The lowest utility bill of $2,900 occurred in November when the machines worked 650 machine hours. Requirements 1. Use the high-low method to calculate the variable cost per machine hour and the total fixed utility cost. 2. Show the equation for determining the total utility cost for the machine shop. 3. If Paul anticipates using 900 machine hours in December, predict the shop's total utility bill using the equation from Requirement 2.