Answer:
See explanation
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://img.qammunity.org/2022/formulas/mathematics/college/45vqw0qu0rlg6jhxlrlqfkjz7nd9fqi3yk.png)
![(70, 80] =>71 - 80](https://img.qammunity.org/2022/formulas/mathematics/college/5pv1956gs9tj1o1t5zezzoxucoq4vboc60.png)
![(80,901]\ =>81 - 90](https://img.qammunity.org/2022/formulas/mathematics/college/4ay103ppsijfop0nomiggfwaljcf5vscyu.png)
![(90,100] =>91 - 100](https://img.qammunity.org/2022/formulas/mathematics/college/c88sh1bxgicesvsnt93yr7csbpf75tosw9.png)
![(100, 110] =>101 - 110](https://img.qammunity.org/2022/formulas/mathematics/college/d4xo67mm2jotdnkmr7dxsfmm2yhkplxdzg.png)
![(110,120] => 111 - 120](https://img.qammunity.org/2022/formulas/mathematics/college/ntplbm6d3n7jd2hwwncxj1qkejl7tn6ku2.png)
The table is as follows:


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

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