In order to calculate marginal cost, producers must compare the difference in the cost of producing one unit to the cost of
purchasing a unit
distributing that urut
producing the next unit
producing a different unit

Identify the example of when situation and time are key to assessing risk of harm in a research study: a study on the efficacy of a behavioral intervention for smoking cessation involves both adults and teenagersasking women if they have had an abortionresearch on the prevalence of hiv-infected individuals in communitiesa survey about sexually transmitted diseases