Which phrase best describes quantity supplied?

The phrase that best describes quantity supplied is "the amount a supplier is willing and able to sell at a given price." This captures the fundamental concept of quantity supplied in microeconomics. Quantity supplied refers to the specific quantity of goods that producers are prepared to offer for sale at a particular price point. It emphasizes the willingness and ability of suppliers to sell, which is influenced by various factors such as production costs, market demand, and price levels.

Understanding this concept is crucial because it delineates how prices can affect supply decisions. As prices rise, suppliers are generally more inclined to increase the quantity supplied since they anticipate greater revenue and profit potential. Conversely, at lower prices, suppliers may scale back the quantity they are willing to sell.

The other options do not accurately encapsulate the definition of quantity supplied. For example, stating "the total available goods in the market" refers more to overall supply rather than the specific quantity that suppliers are willing to sell at a certain price. Similarly, mentioning "the change in supply over time" focuses on the dynamics of supply shifts rather than the specific interaction between price and quantity supplied, while "the difference in price levels" addresses price variations without relating directly to the quantity that suppliers are willing to sell.