From the given table the values of a, b and c are :

1. a = 16, b = 52 and c = 8

2. a = 16, b = 12 and c = 8

3. a = 40, b = 52 and c = 60

4. a = 40, b = 12 and c = 60

The cumulative curve for a frequency distribution starts from :

1. 0

2. $\dfrac{\text{upper limit + lower limit}}{2}$

3. lower limit of 1st class

4. $\dfrac{\text{lower limit - upper limit}}{2}$

The cumulative curve for a frequency distribution terminates at :

1. 100

2. $\dfrac{\text{upper limit + lower limit}}{2}$

3. $\dfrac{\text{lower limit + upper limit}}{2}$

4. upper limit of last class

The cumulative frequency of the class 70-90 is :

1. 80

2. 120

3. 180

4. 40