If the marginal propensity to consume is 0.8, full-employment output is $14 trillion, and current output is $13.5 trillion, then investment spending must to reach full-employment output

The goal of an economist who formulates new theories is to a. provide an interesting framework of analysis, whether or not the framework turns out to be of much use in understanding how the world works. b. provoke stimulating debate in scientific journals. c. contribute to an understanding of how the world works. d. demonstrate that economists, like other scientists, can formulate testable theories.