Find the missing numbers ($A$ and $B$) in the series and find the value of $B-A$.
$$11,22,33,A,55,66,77,B$$

Let's analyze the given number series:
$$11,22,33,A,55,66,77,B$$

The terms are consecutive multiples of $11$:

* $11\times 1=11$
* $11\times 2=22$
* $11\times 3=33$

Following this arithmetic pattern, the fourth term $A$ must be:

$$A=11\times 4=44$$

The series continues as:

* $11\times 5=55$
* $11\times 6=66$
* $11\times 7=77$

Thus, the eighth term $B$ must be:

$$B=11\times 8=88$$

Now, we need to calculate the value of $B-A$:

$$B-A=88-44=44$$