Twenty people leaving a cinema are each asked, “How many times have you attended the cinema in the past year?” Their responses are:

6, 2, 13, 1, 4, 8, 11, 3, 4, 16, 7, 20, 13, 5, 15, 3, 12, 9, 26 and 10.

Construct a stem-and-leaf diagram for these data and include a key.