Detailed Answer
Answer (B) is correct. The minimum charge would include any variable costs incurred plus depreciation on a straight-line basis. Currently, variable costs are $360,000 at 60% of capacity ($1,800,000 ’ 20%). If Quigley purchases energy equal to an additional 30% of capacity, it can be assumed that the increase in total variable costs will be half of the variable costs for 60% of capacity, or $180,000. Also, allocating $21,000,000 over 14 years results in an annual depreciation of $1,500,000. Of this amount, 30% will relate to the capacity sold. Thus, the depreciation charge to Quigley is
$450,000 ($1,500,000 ’ 30%). The total charge is $630,000 ($450,000 depreciation + $180,000 VC).