The ability to think logically about hypothetical situations is indicative of the stage of development.

 Formal operational stage. It is like the formation of common sense which begins at the age of twelve until adulthood. It is the ability to think about abstract concepts. This happens when a person can do calculations in math, think creatively, reason out without any dependence on concrete manipulation.

Currently, as of february 2016, an american traveling in france would be by the exchange rate. the weakness of the euro and the strength of the us dollar means that items in france cost less to an american than they otherwise would. of course, if this trend reverses and the us dollar weakens and the euro strengthens, such as was happening in early 2008, an american traveling in france would have an adverse experience because items would cost relatively more.