see attachment and explain it

Approach: we’ll first satisfy the condition given in the question.

Answer:
For filling each row with four letters taken at random, choices are 4.
So in 4! ways.

Now, we are free to fill the blocks with the letters taken at random.

We have 8 blocks left to be filled by 4 letters.

So Number of ways to do that= 8.7.6.5

The two conditions are ANDed, so multiply.

After this 2 things have to be kept in mind and be included in the answer:
(i)the number of ways in which the letters of the word can be selected
(ii)the number of ways in which the letters assigned to a row be internally arranged.

which can be done by using the fundamental principle of multiplication.