Averages and measures of spread — practice question

A stem-and-leaf diagram summarises how many items each of 22 supermarket customers bought. It shows: Stem 1: leaves 1, 3, 6, 6 Stem 2: leaves 0, 2, 2, 2, 4, 8, 9 Stem 3: leaves 1, 1, 5, 8, 9, 9 Stem 4: leaves 2, 4, 6, 7, 8 Key: $1 | 1$ means 11 items.