Mean

A class of 35 students sat for a Science test marked out of 30. Their marks are grouped as follows:

- 10 ≤ x < 16 : 8 students
- 16 ≤ x < 22 : 15 students
- 22 ≤ x ≤ 30 : 12 students

Estimate the mean mark of the class, using the midpoints of each class interval.