question_answer

The given table shows the number of packets arrange by 24 students in a day in a there classroom.

Number of Packets	Number of Students \[({{f}_{i}})\]	Class mark \[{{y}_{i}}\]	\[{{d}_{i}}={{y}_{i}}-a\]	\[{{f}_{i}}{{d}_{i}}\]
50 - 60	f'			- 60
60 - 70	f"
70 - 80	5			0
80 - 90	2f'
90 - 100	f" - 2

What is the mean number of packets arrange by students in the class?

A)  56                               

B)  66           

C)  78                               

D)  76