How many meaningful words can be made from the letters $AEHT$,using each letter only once?

If it is possible to make a meaningful word with the second,the fifth and the eighth letters of the word $CARETAKER$,which of the following will be the first letter of that word? If no such word can be made,give $X$ as the answer. If more than one such word can be made,give $M$ as the answer.

How many $D$'s are there in the following series which are immediately followed by $W$ but not immediately preceded by $K$?
$K, D, C, W, K, D, W, N, K, G, D, W, W, D, H, K, V, D, W, Z, D, W$

How many such pairs of letters are there in the word $PROFITABLE$,each of which has as many letters between them in the word as in the English alphabet?

If each alternate letter beginning with the first in the word $WORKING$ is replaced by the next letter in the English alphabet and each of the remaining letters is replaced by the previous letter in the English alphabet,which of the following will be the fourth from the right end after the replacement?

Each of the following questions is based on the following alphabet series.
$A, B, C, D, E, F, G, H, I, J, K, L, M$
$N, O, P, Q, R, S, T, U, V, W, X, Y, Z$
If the first and the second letters interchange their positions,and similarly the third and the fourth letters,the fifth and the sixth letters,and so on,which letter will be the seventeenth from your right?