Answer:
See explanation
Step-by-step explanation:
The question says the diameters of 50 pillars were measured. However, only the measurements of 20 pillars were provided.
So, I will work with 20
Given





Solving (a): Frequency distribution table
Using the given intervals:
![(60,70]\ => 61 - 70](https://tex.z-dn.net/?f=%2860%2C70%5D%5C%20%3D%3E%2061%20-%2070)
![(70, 80] =>71 - 80](https://tex.z-dn.net/?f=%2870%2C%2080%5D%20%3D%3E71%20-%2080)
![(80,901]\ =>81 - 90](https://tex.z-dn.net/?f=%2880%2C901%5D%5C%20%3D%3E81%20-%2090)
![(90,100] =>91 - 100](https://tex.z-dn.net/?f=%2890%2C100%5D%20%3D%3E91%20-%20100)
![(100, 110] =>101 - 110](https://tex.z-dn.net/?f=%28100%2C%20110%5D%20%3D%3E101%20-%20110)
![(110,120] => 111 - 120](https://tex.z-dn.net/?f=%28110%2C120%5D%20%3D%3E%20111%20-%20120)
The table is as follows:


The class mark is the average of the class interval
For instance: The class mark of 61 - 70 is:

<em>This is applied to other intervals</em>
Solving (b): The histogram
<em>See attachment for histogram</em>
The frequency is plotted on the y-axis while the class interval, on the x-axis.