Me and my friends are from Europe, we went to US. At the end of the trip they bought an item worth $USD 100$, but because they were short of money, so I paid for the item first with my own $USD 100$.
After we came back from Europe, they would have to pay me. They would like to pay me in EUR. What is the fair amount of EUR they should pay me?
Assuming that at money exchange counter, the rates are as follow ( buy/sell are from their perspective):
1 USD buys 1 EUR
1 EUR buys $\frac{1}{1.05}$ USD.