If you have 7 sets of numbers
$\displaystyle
\left (4,4,3,3 \right )=A$
$\displaystyle \left (NA,NA,4,4 \right )=B$
$\displaystyle \left (4,3,4,2 \right )=C$
$\displaystyle \left (4,4,4,5 \right )=D$
$\displaystyle
\left (3,3,4,4 \right )=E$
$\displaystyle \left (2,4,3,3 \right )=F$
$\displaystyle \left ( 4,4,4,4 \right )=G$

If we find the mean each set, then find the mean of all the sets to that:
(S=total # of sets M=mean)

$\displaystyle \frac{A+B+...+G}{S}=M$

How would we account for the two missing values in B?
Would it be wrong to only use the two values?