The collection of all possible combinations of the goods and services that can be produced from a given amount of resources and a given stock of technological knowledge is called the ____________ of the economy.
The process that occurs when physical forces break rock into smaller pieces without changing the rock's chemical composition is called mechanical weathering.
The age of the father 4 years ago was 8 times the age of his son. At present, the father's age is 4 times that of his son. Find the present age of son.