Which of the following describes resource mobility as assumed by the classical theories of international trade?
a. it is the expectation that all resource-based transactions will have no foreign exchange complications.
b. it is the notion that countries should share their resources freely with other countries.
c. it is the assertion that all resources of a nation should be directly controlled by the government.
d. it is the assumption that a resource used in producing a product for one industry can be shifted and put to use in another industry.

Employees at a library check out books to patrons. books have an isbn and a name. the library sometimes has multiple copies of the same book. books have one or more authors. a patron is an individual who has an active (non-expired) library card. for each library card, we store the person's first and last names and their address. for each employee, we store their employee id, current salary, first and last name and their address. we also store the employee id of their current manager. each time we check out a book to a patron we need to store the date of the transaction, the employee who checked out the book to the patron, and the library card of the patron. some employees have library cards. if an employee patron turns in a book late, the fine that they pay is a percentage of their salary. some employees are authors who have library cards—they are allowed to check out as many books as they like.