Mean

The masses of 60 apples are grouped as follows:

25 < x ≤ 35 : frequency 8

35 < x ≤ 45 : frequency 14

45 < x ≤ 55 : frequency 20

55 < x ≤ 65 : frequency 18

Using midpoints 30, 40, 50 and 60, find the mean mass of the apples.