The First-In, First-Out (FIFO) method is an accounting practice where the cost of the oldest inventory items is assigned to the cost of goods sold (COGS). This method is widely used because it often reflects the actual physical flow of goods, especially for perishable items. During periods of inflation, FIFO typically results in higher reported net income because older, cheaper costs are matched against current revenues.

A write-off is an accounting action that reduces the book value of an asset to zero or a lower amount, recognizing it as an expense or loss on the income statement. This is typically performed when an asset, such as a bad debt or obsolete inventory, is deemed to have no future economic value to the firm.

Total cost consists of fixed and variable costs. Since fixed costs remain constant at 200, any change in total cost is entirely due to the change in variable costs. The increase from 500 to 600 represents a 100 unit increase in variable costs, confirming that variable cost rises by 100.

Cost accounting is a specialized branch of accounting that records, summarizes, and analyzes a company's production costs. It helps management make informed decisions regarding pricing, budget control, and operational efficiency by identifying where resources are being consumed within the production process.

A firm should shut down in the short run if its total revenue is insufficient to cover its variable costs. If revenue exceeds variable costs, the firm can at least pay for its operating expenses and contribute toward fixed costs, which must be paid regardless of production. If variable costs exceed revenue, the firm loses more money by operating than by shutting down completely.

Freight refers to the goods transported in bulk by truck, train, ship, or aircraft. In commercial and economic terms, the 'freight' also denotes the price or fee paid for the carriage of these goods. It is a critical component of logistics costs, influencing the final price of commodities in the market by accounting for the distance and mode of transport utilized in the supply chain.

Wages are a variable cost of production. An increase in wages directly raises the marginal cost of producing each additional unit. Since firms maximize profit where MR=MC, an upward shift in the MC curve will result in a lower profit-maximizing quantity of output, assuming the marginal revenue curve remains unchanged.

The marginal cost curve reflects the change in total cost resulting from an additional unit of output. Initially, increasing marginal product causes marginal costs to decline. As diminishing marginal returns set in, marginal costs begin to rise. This combination of falling and then rising costs creates the characteristic U-shape of the marginal cost curve.

The average cost is calculated by dividing the total cost by the number of units. For n=10, total cost is 2000 + 100(10) = 3000. Average cost is 3000/10 = 300. The provided answer 'C' claims the result is 1300, which is mathematically inconsistent with the provided cost function. The conflict between the calculation and the provided answer is noted.

The source identifies the point where Average Revenue equals Average Variable Cost as the point of normal profit. However, standard economic theory defines normal profit as the point where Average Revenue equals Average Total Cost (ATC). The provided answer likely refers to the 'shutdown point' rather than the normal profit point.