Exchange rate is the rate at which one country's currency is changed for another country's currency. For example the rate at which one dollar can be changed for pound sterling or any other currency.
People and businesses can ask for loans (borrowed money generally from a bank, but can be from an organization, person, etc.). The one who asked for a loan must return the exact money PLUS an extra...
That depends on what you DO know. You might consider asking again, being more specific about what information you have. For example, if you know the amount of interest, the principal, and the length...