The letters of the word OUGHT are written in all possible ways and these words are arranged as in a dictionary, in a series. Then the serial number of the word TOUGH is
(A)Arrange the letters of OUGHT in alphabetical order: G, H, O, T, U.
(B) Count words starting with each letter before ""T"":
\[
G \to 4!, \quad H \to 4!, \quad O \to 4!.
\]
(C) Count words starting with ""T"" but second letter as:
\[
TG \to 3!, \quad TH \to 3!, \quad TOG \to 2!, \quad TOH \to 2!.
\]
(D) Add the counts:
\[
4! + 4! + 4! + 3! + 3! + 2! + 2! + 1! = 89.
\]