What best describes aggregate supply?

The correct answer effectively defines aggregate supply as the total supply of goods and services that firms plan to sell in an economy at a given overall price level during a specific time period. This reflects the production capacity and intentions of firms based on various factors, including input costs, technology, and government policies.

By understanding aggregate supply, one can analyze how factors such as changes in resource prices or productivity improvements can shift the aggregate supply curve, impacting overall economic output and pricing levels. This concept is crucial in macroeconomic analysis because it helps in assessing potential economic growth and inflation rates.

The other options do not accurately represent aggregate supply. For instance, the combined demand for goods and services refers to aggregate demand, while the total amount of money in circulation pertains to the money supply, neither of which aligns with the definition of aggregate supply. Additionally, stating the number of goods and services available at a certain price is more about microeconomic supply, focusing on specific markets rather than the broader economy.