Answer: (a) 9
Step-by-step explanation:
We are given that ,
The first two classes of a frequency distribution are 0-9 and 10-19.
We know that the class width of an class interval is basically the difference between the upper limit and the lower limit of the interval.
For example the class interval for interval 40 - 45 is 5 because 45-40=5.
For the given class interval 0-9 , upper limit= 9
Lower limit =0
⇒ Class width = 9-0= 9
Similarly , for 10-19 , the class width = 19-10=9
Therefore , the class width is 9 .
Hence, the correct answer is (a) 9.
. So plugging in the coordinates we have 
