Answer:
when the benefits outweigh the costs
Explanation:
The social exchange theory is the theory that looks at social interaction between parties which judge the risks and benefits of an exchange by doing a cost-benefit analysis.
According to this theory the cost-benefit analysis is done by people in all types of social exchanges. If a person in a relationship gives effort in the relationship but it is not reciprocated by the other person the relationship is likely not to succeed according to this theory. So, the benefits need to outweigh the cost in order for a person to help another person.
