What is the definition of gross domestic product (gdp)?
a. an indicator used to measure the overall happiness of citizens based on their community involvement
b. the total value of officially recorded goods and services produced in a country's borders within a given year
c. the monetary worth of goods and services produced in a country, plus income earned from investments outside of the country
d. the total value of officially recorded goods and services produced by companies and citizens, both inside and outside a country's borders, within a given year