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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def workdays(first_day=None):
 """Returns a list of workday names. Arguments --------- first_day : str, default None The first day of the five-day work week. If not given, 'Monday' is used. Returns ------- list A list of workday names. """

    if first_day is None:
        first_day = 'Monday'
    ix = _lower_weekdays().index(first_day.lower())
    return _double_weekdays()[ix:ix+5]