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L P6-4. High-Low and Cost Formula Harrison Company has accumulated the following total manufactur- ing overhead costs for two levels of activity within the relevant range): Low High 130,000 $628,000 Activity (direct labor hours).... Total manufacturing overhead 90,000 $484,000 The total overhead cost includes variable, fixed, and mixed costs. At 130,000 direct labor hours, the total cost breakdown is as follows: Variable cost. Fixed cost. Semi-mixed cost. $286,000 85,000 257,000 Required a. Using the high-low method of cost analysis, determine the variable portion of the semi-variable cost per direct labor hour. Determine the total fixed cost component of the mixed cost. b. What should the total planned overhead cost be at 115,000 direct labor hours