Which stadiums have an average attendance of 13840?
{'header': ['Team', 'Stadium', 'Capacity', 'Lowest', 'Highest', 'Average'], 'page_title': '2007–08 Scottish Premier League', 'page_id': '', 'types': ['text', 'text', 'real', 'real', 'real', 'real'], 'id': '1-11208143-9', 'section_title': 'Attendances', 'caption': 'Attendances', 'rows': [['Celtic', 'Celtic Park', '60832', '45000', '60000', '56676'], ['Rangers', 'Ibrox Stadium', '51082', '47419', '50440', '49143'], ['Heart of Midlothian', 'Tynecastle Stadium', '17420', '10512', '17131', '15930'], ['Hibernian', 'Easter Road', '17500', '7650', '17015', '13840'], ['Aberdeen', 'Pittodrie', '22199', '8240', '17798', '11993'], ['Dundee United', 'Tannadice Park', '14209', '5845', '13613', '8530'], ['Motherwell 1', 'Fir Park', '13742', '4259', '10445', '6598'], ['Kilmarnock', 'Rugby Park', '18128', '4086', '11544', '6181'], ['Falkirk', 'Falkirk Stadium', '6935', '4490', '6803', '5567'], ['Inverness CT', 'Caledonian Stadium', '7500', '3420', '7753', '4752'], ['St. Mirren', 'Love Street', '10800', '3163', '7840', '4547']], 'name': 'table_11208143_9'}