def stories(firm, date, mdatabase):
    """
    Number of articles published on date tagged with firm that have
    relevance score greater than 70%
    Relies on column structure of mdatabase
    Returns INTEGER
    """
    if (firm, date) in mdatabase.stor:
        return mdatabase.stor[(firm, date)]
    matches = len(mdatabase.tdMap.get((firm, date), []))
    mdatabase.stor[(firm, date)] = matches
    return matches