The width of each of nine classes in a frequency distribution is 2.5 and the lower class boundary of the lowest class is 10.6. Which of the following is the upper class boundary of the highest class?

1. 28.1

2. 30.6

3. 33.1

4. 35.6

In a histogram, the area of each rectangle is proportional to :

1. the class-mark of the corresponding class-interval

2. the class-size of the corresponding class-interval

3. frequency of the corresponding class-interval

4. cumulative frequency of the corresponding class interval

In the 'less than' type of ogive, the cumulative frequency is plotted against :

1. the lower limit of the concerned class interval

2. the upper limit of the concerned class interval

3. the mid-value of the concerned class interval

4. any value of the concerned class interval