<prompt> Human: I live in the US and my parents live in Canada. They will be visiting me this summer. They have asked me to cover their expenses while they are in the US visiting, since the Canadian dollar is at an all time low 1 USD 0.75 CAD. They said they will pay me back in USD when the exchange rate improves. Heres an example: If my parents owe me 300 USD today, with an exchange rate of 0.75, that equates to 400 CAD. However, if they wait for say an exchange rate of 0.8, that equates to 375 CAD. All for the original 300 USD amount. They save 25 CAD.Is this fair? If not, can you please explain why?  <response>: The math is correct, but that doesnt necessarily make it fair. What if the rate drops? What if it takes 18 months to go up? Are you ok with giving them an interest-free loan for X months? 