Queuing (waiting-line) models minimize, for a given rate of arrivals, the sum of (1) the cost of providing service (including facility costs and operating costs) and (2) the cost of idle resources waiting in line. The latter may be a direct cost, if paid employees are waiting, or an opportunity cost in the case of waiting customers. This minimization occurs at the point where the cost of waiting is balanced by the cost of providing service.

Job-order costing is used by companies whose products or services are readily identified by individual units or a specific job, each of which receives varying amounts and types of input. The dissimilarity of the various loan services provided make job-order costing appropriate.

A voluntary change in accounting policy is applied retrospectively unless it is impracticable to determine period-specific effects or the cumulative effect. Retrospective application means adjusting the opening balances of equity for the first period presented and restating other comparative amounts.

The relevant costs of making the motor are direct materials, direct labor, variable manufacturing overhead, rental costs of the special machinery, and rental costs of the new warehouse. The fixed manufacturing overhead and the costs of the current warehouse space are not relevant because they will be incurred regardless of whether the motor is made or bought. Buying the motor will cost US $630,000 30,000 x $21).
Making the motor will cost US $549,000 {[30,000 x $8 DM +$ 4 DL + $3 VOH)] +$54,000 + $45,000}. Hence, making the motor saves US $81,000 $630,000 - $549,000). A manufacturing company is considering a new product for the coming year, which is an electric motor the company can purchase from a reliable vendor for US $21.00 per unit. The alternative is t. manufacture the motor internally. The company has excess capacity to manufacture the 30,000 motors needed in the coming year except for manufacturing space and special machinery. The machinery can be leased for US $45,000 annually. Finished goods warehouse space adjoining the main manufacturing facility, leased for US $39,000 annually, can be converted and used to manufacture the motors. Additional offsite space can be leased at an annual cost of US $54,000 to replace the finished goods warehouse. The estimated unit costs for manufacturing the motors internally, exclusive the leasing costs itemized above, are:

The quantity of inventory on hand is represented by they axis and time by the axis. The reorder lead time is represented by the line segment BC. The diagram presented represents the economic circler quantity ECQ) model.