Famine, Affluence Morality

In "Famine, Affluence, and Morality",[7] one of Singer's best-known philosophical essays, he argues that the injustice of some people living in abundance while others starve is morally indefensible. Singer proposes that anyone able to help the poor should donate part of their income to aid poverty and similar efforts. Singer reasons that, when one is already living comfortably, a further purchase to increase comfort will lack the same moral importance as saving another person's life. Singer himself donates 20% of his salary to Oxfam and UNICEF. In "Rich and Poor", the version of the aforementioned article that appears in the second edition of Practical Ethics,[8] his main argument is presented as follows: If we can prevent something bad without sacrificing anything of comparable significance, we ought to do it; absolute poverty is bad; there is some poverty we can prevent without sacrificing anything of comparable moral significance; therefore we ought to prevent some absolute poverty.

( Above is from Wikepedia)

Now, how does this relate to giving money overseas? My argument has two steps.