In the formula $\bar{x} = A + \frac{\Sigma f_{i} u_{i}}{\Sigma f_{i}} \times c$ for the mean,$u_{i} = \ldots \ldots \ldots$

In the formula $\bar{x} = \frac{\Sigma f_{i} x_{i}}{\Sigma f_{i}}$,$\Sigma f_{i}$ represents ........

The daily income of a sample of $50$ employees is tabulated as follows:

Income (in $Rs.$)	$1-200$	$201-400$	$401-600$	$601-800$
Number of employees	$14$	$15$	$14$	$7$

Find the mean daily income of the employees. (in $.5$)

In calculating the mean of grouped data,grouped in classes of equal width,we may use the formula $\bar{x} = a + \frac{\sum f_i d_i}{\sum f_i}$,where $a$ is the assumed mean. $a$ must be one of the mid-points of the classes. Is the last statement correct? Justify your answer.

For a given frequency distribution,$\Sigma f_{i} u_{i} = -13$,$n = \Sigma f_{i} = 100$,$A = 62.5$ and $c = 15$. Then,mean $\bar{x} = \dots$

For a given frequency distribution,$\Sigma f_{i} d_{i} = -50$,$\Sigma f_{i} = 200$ and $A = 62.5$. Then the mean $\bar{x} = $ ........