Pecuniary economies refer to the cost savings that a production firm can achieve through various factors. These cost savings can arise from different sources, such as large scale production, purchasing and market economies, indivisibility of factor inputs, and learning economies of workers and managers. Among these options, the correct answer is option 'B' - purchasing and market economies.

Purchasing and market economies refer to the cost savings that a firm can achieve by purchasing inputs at a lower cost and by taking advantage of favorable market conditions. Here is a detailed explanation of why purchasing and market economies contribute to pecuniary economies for a production firm:

1. Purchasing Economies: When a firm buys inputs in bulk or in large quantities, it can negotiate better prices with suppliers. This is because suppliers are more likely to offer discounts or lower prices to firms that can guarantee a consistent and substantial demand. By purchasing inputs at a lower cost, the firm can achieve cost savings and increase its profitability.

2. Market Economies: Market economies arise from the competition among suppliers in the market. When there is intense competition, suppliers often reduce their prices to attract customers. This allows the firm to purchase inputs at a lower cost and achieve cost savings. In addition, market economies also refer to the availability of substitute inputs in the market. If there are multiple suppliers offering similar inputs, the firm can choose the most cost-effective option, leading to further cost savings.

3. Economies of Scale: Although not mentioned in the given options, economies of scale also contribute to pecuniary economies. Large scale production refers to the production of goods or services in large quantities. When a firm produces on a large scale, it can spread its fixed costs over a larger output, resulting in lower average costs per unit. This allows the firm to achieve cost savings and increase its profitability.

In conclusion, purchasing and market economies contribute to pecuniary economies for a production firm by allowing it to purchase inputs at a lower cost and take advantage of favorable market conditions. These cost savings can lead to increased profitability for the firm.