code: @Override
      public WorkingWeek getWorkingWeek(final String currency) {
          final WorkingWeek workingWeek = workingWeeks.get(currency);
          return workingWeek != null ? workingWeek : WorkingWeek.DEFAULT;
      }
docs: Return a default Mon-Fri for most, but some might be Sun-Thu (Arabic countries).
  @param currency
  @return the WorkingWeek registered for this currency other the default Mon-Fri.