If someone could explain how he determined these intervals it would be extremely helpful!

Problem 1: In an experiment, the life times of ball bearings were recorded (million revolutions).

Consider the following 22 observations (sorted in order):

17.88, 28.92, 33.00, 41.52, 42.12, 45.60, 48.48, 51.84, 51.96, 54.12,

55.56, 67.80, 68.64, 68.88, 84.12, 93.12, 98.64, 105.12, 105.84, 127.92,

128.04, 173.40.

3. Construct the histogram for the data.

To construct histogram one needs to group the data into a number of equally

spaced intervals. For example, if decide for five intervals that have for the

midpoints:

33.4, 64.5, 95.6, 126.7, 157.9

then the counts of the data in these bins are:

7, 7, 5, 2, 1 < I don't understand where these came from aswell?