# File lib/currencies/exchange_bank.rb, line 30
    def exchange(cents, from_currency, to_currency)
      rate = get_rate(from_currency, to_currency)
      if rate
        (cents * rate).floor
      else
        from_currency = ISO4217::Currency.from_code(from_currency)
        to_currency = ISO4217::Currency.from_code(to_currency)
                
        if from_currency && to_currency && from_currency.exchange_rate && to_currency.exchange_rate && (from_currency.exchange_currency == to_currency.exchange_currency)
          ((cents * from_currency.exchange_rate) / to_currency.exchange_rate).floor
        else
          raise Money::UnknownRate, "No conversion rate known for '#{from_currency}' -> '#{to_currency}'"
        end
      end
    end