Which of the following tools helps a producer set up an efficient system of production?
O A. A determination of opportunity costs.
O B. An electric-powered assembly line.
O C. A production possibilities frontier graph.
O D. A market research department.

What is the difference between a journal entry written by an eyewitness to an event and a play written about the same event? a. the journal entry is a historiographical source, while the play is a periodical source. b. the journal entry is a chronological source, while the play is a primary source. c. the journal entry is a primary source, while the play is a secondary source. d. the journal entry is a secondary source, while the play is a periodical source.