What is the place for paying the expiation for a vow broken in a country other than the vower's home country?

If the vow is accompanied by an oath, then after breaking it, an expiation for an oath is due: feeding ten needy persons from the average of what you feed your own families, or clothing them, or emancipating a slave. And whoever cannot find [the means] then [is] a fast of three days. The feeding should be from the average of what a man feeds his family in whatever country they live in at the time of giving the expiation. However, if the vow is not accompanied by an oath, there is no expiation.