The enrollment of a school during six consecutive years was as follows:

1620, 2060, 2540, 3250, 3500, 3710.

Find the mean enrollment.

Find the mean of the first twelve natural numbers.

Find the mean of the first seven odd prime numbers.

The marks (out of 100) obtained by a group of students in a Mathematics test are 81, 72, 90, 90, 85, 86, 70, 93 and 71. Find the mean marks obtained by the group of students.