hey ! i am looking for a train from cambridge to stevenage .
{'service': 'train', 'act': 'inform', 'slot_name': 'leave', 'value': 'every 2 hours'} {'service': 'train', 'act': 'request', 'slot_name': 'arrive', 'value': '?'} {'service': 'train', 'act': 'request', 'slot_name': 'leave', 'value': '?'}
trains depart approximately every 2 hour -s . what time would you like to leave and arrive by ?