A group frequency table with class intervals of equal sizes using $250-270(270$ not included in this interval) as one the class interval is constructed for the following data:

$268,220,368,258,242,310,272,342,310,290,300,320,319,304,402,318,406,292,354,278,210,240,330,316,406,215,258,236$
The frequency of the class $310-330$ is

A grouped frequency distribution table with classes of equal sizes using $63-72$($72$ included) as one of the class is constructed for the following data:
$30,32,45,54,74,78,108,112,66,76,88,40,14,20,15,35,44,66,75,84 95,96,102,110,88,74,112,14,34,44$.

The number of classes in the distribution will be

To draw a histogram to represent the following frequency distribution:

The adjusted frequency for the class $25-45$ is:

If the mean of the observations $x, x+3, x+5, x+7, x+10$ is $9,$ the mean of the last three observations is