Final answer:
In the calculation of GDP, a used tractor sold to a corn farmer would be omitted because it does not represent new production within the economy. Other examples such as childcare provided by a grandmother or the rise in life expectancy are also excluded from GDP calculations. The correct option is a.
Step-by-step explanation:
When considering what is included in the calculation of Gross Domestic Product (GDP), it's important to understand that GDP measures the value of final goods and services produced within a country's borders within a certain time frame. Sales of used goods, such as a used tractor, do not contribute to current production and are omitted from the calculation of GDP. Therefore, from the choices provided: a can of corn sold at a convenience store, a used tractor sold to a corn farmer, a corn muffin mix sold at a farmer's market, and five ears of corn sold at a supermarket, the GDP would omit the sale of the used tractor. This is because the used tractor is not a new production and as such, does not represent a part of the country's economic activity within that time period.
Other items that are not included in GDP are non-market transactions, such as child care provided by a grandmother, and the rise in life expectancy over time as these do not represent a market transaction. On the other hand, the cost of hospital stays, child care provided by a licensed daycare center, a new car sale, and the value added by goods in the production chain captured in the final products are included.