 A similar case of effective altruism is the following: By donating $0 you save no one; by donating $50 you save 1 person; by donating $5000 you save 500 people (which is proportionate to the previous option); by donating $10,000 you save 101 (which is irrational and a waste of money in comparison to the previous option); by donating $10,050 you save 200 people (Wessels 2015, p. 90). Now, although the last option is very "effective" and makes excellent use of the extra $50 (in comparison to the second option), the question is whether adding the extra $50 donated by the generous donor who gives $10,000 is obligatory. The poor person is commended for his supererogatory act of giving $50 to save one person; cannot we regard the extra $50 of the rich person who donated $10,000 as his duty, especially in light of the possibility of saving 100 more people by this small sum? Once you donate $10,000 it is reasonable to expect of you to give the extra marginal addition of another $50 so as to double the benefit of your donation (i.e. saving 200 people). This demonstrates that the threshold conception of the supererogatory as everything lying beyond the obligatory requires some refinement. There are circumstances in which in the realm of the supererogatory some new obligations may be created (Wessels 2015). As we have seen, such circumstances exist in the case of promises: promising itself is supererogatory; but once a promise is made, actions fulfilling the promise become obligatory.