Which of the following is included in personal income but not in national income?

A nonlinear function

A) makes little sense, because variables in the real world are related linearly. B) can be adequately described by a straight line between the dependent variable and one of the explanatory variables. C) is a concept that only applies to the case of a single or two explanatory variables since you cannot draw a line in four dimensions. D) is a function with a slope that is not constant.

Firms in an industry will not earn long-run economic profits if:

A. Fixed costs are zero B. The number of firms in the industry is fixed C. There is free entry and exit of firms in the industry D. Production costs for a given level of output are minimized