Decision-making outcomes are typically evaluated using both quantitative and qualitative factors. Quantitative factors are measurable in numerical or monetary terms, such as costs and revenues. Qualitative factors, while not easily quantified, include intangible elements like employee morale, brand reputation, or customer satisfaction. Both types of information are essential for a comprehensive analysis of any business decision.

Opportunity cost represents the potential benefit that is given up when one alternative is selected over another. It is a fundamental concept in economics and cost accounting, representing the value of the next best alternative use of resources that was not chosen, which is essential for informed decision-making.

Past costs, often referred to as sunk costs, are expenditures that have already been incurred and cannot be recovered or altered by any decision made in the present or future. Because they remain the same regardless of which alternative is chosen, they are considered irrelevant for decision-making purposes and should be ignored to avoid biased or incorrect financial conclusions.

The original cost of obsolete inventory is classified as a sunk cost because it represents an expenditure already incurred in the past. Since this cost cannot be recovered or altered by any future decision regarding the disposal or retention of the items, it is considered irrelevant for current decision-making processes. Sunk costs should be excluded from analysis when determining the most efficient path forward for existing assets.

A decision method is a systematic approach used by management to evaluate various alternatives. It integrates quantitative data, such as financial projections and cost-benefit analysis, with qualitative factors, such as strategic alignment, employee morale, and market reputation. By utilizing a formal decision-making framework, organizations can reduce uncertainty, ensure consistency in their choices, and align their actions with long-term business objectives and operational goals.

Relevant costs are those future costs that differ among the various alternatives being considered. They are the only costs that impact a company's decision-making process. By focusing on relevant costs, managers can filter out noise and concentrate on the financial data that will actually change based on the decision made, which is vital for accurate financial analysis and strategic planning.

Qualitative factors are non-monetary elements that influence business decisions but cannot be expressed in numerical terms in the books of accounts. Examples include employee morale, corporate culture, brand image, and customer loyalty. While these factors are difficult to measure, they are critical for long-term strategic success and must be considered alongside quantitative data during the decision-making process.

The decision-making process typically begins with defining the problem. The second step involves gathering all relevant data and information necessary to analyze the situation. Obtaining accurate and timely information is crucial for evaluating alternatives effectively and ensuring that the final decision is based on a solid foundation of facts and figures.

The change in operating income is calculated by multiplying the change in units sold by the contribution margin per unit. By rearranging this formula, the change in units is the change in operating income ($9,000) divided by the contribution margin per unit ($6,000), resulting in 1.5 units.

The contribution margin per unit is defined as the selling price per unit minus the variable cost per unit. This figure is fundamental in cost-volume-profit analysis as it represents the amount of revenue from each unit sold that is available to cover fixed costs and contribute to the company's overall operating income.