Activity-Based Costing (ABC) is a sophisticated accounting method that identifies activities within an organization and assigns the cost of each activity to all products and services according to the actual consumption by each. By creating a hierarchical structure of activities, ABC provides a more precise allocation of overhead costs compared to traditional volume-based costing systems, leading to better decision-making regarding product profitability and resource management.

In activity-based costing, resource consumption is driven by various factors. A product's demand for support activities is influenced by the size of production batches, the inherent complexity of the product design, and the number of distinct process steps required to manufacture it. All these elements necessitate different levels of overhead support, making them critical drivers in an ABC system.

A cost hierarchy is a framework used in activity-based costing to categorize costs into different levels, such as unit-level, batch-level, product-sustaining, and facility-sustaining costs. This structure helps in selecting appropriate cost drivers for each pool, ensuring that costs are allocated based on the actual consumption of resources, which leads to more accurate product costing and better management decision-making.

Absorption costing includes fixed manufacturing overheads in product costs, leading to the calculation of production volume variance when actual production deviates from the budgeted level. Variable costing, however, treats fixed overheads as period costs, thus excluding this variance from the product costing process.

The budgeted denominator level is calculated by dividing the total budgeted fixed costs by the budgeted fixed cost per unit. In this scenario, $55,000 divided by $55 per unit equals 1,000 units. This denominator level represents the volume of production used to allocate fixed manufacturing overheads to products under absorption costing, ensuring that the total fixed costs are fully absorbed at the planned level of activity.

In absorption costing, the volume production variance (or production volume variance) arises from the difference between the budgeted production level (the denominator level) and the actual production level. The choice of the denominator level is critical because it determines the fixed overhead allocation rate, which directly impacts the variance calculation.

In standard absorption costing, if the production volume variance is calculated as the difference between budgeted and actual production, it is often treated as a period cost or adjusted against cost of goods sold. The source answer suggests it 'must not exist' in certain contexts, which may refer to specific theoretical models where variances are fully absorbed.

Under absorption costing, when production is less than sales, the company sells more units than it produces during the period. This leads to the release of fixed manufacturing overhead costs previously deferred in beginning inventory. Consequently, the cost of goods sold includes both current period costs and costs from prior periods, which generally results in a lower reported operating income compared to variable costing, where fixed costs are expensed as incurred.

In absorption costing, fixed manufacturing overhead is allocated to each unit produced. When production exceeds sales, a portion of these fixed costs is deferred in ending inventory rather than being expensed. Consequently, producing more units than are sold increases the amount of fixed costs capitalized in inventory, thereby artificially inflating the reported operating income for that period.

Under absorption costing, fixed manufacturing overhead is allocated to units produced, which can defer costs into inventory. When production levels are high, more fixed costs are capitalized in ending inventory rather than expensed. This results in a higher reported profit compared to variable costing, often creating a scenario where the production volume exceeds the breakeven sales volume required to cover all costs, as fixed costs are effectively spread over more units.