If all the words with or without meaning made using all the letters of the word "KANPUR" are arranged as in a dictionary, then the word at 440th position in this arrangement is:
Arranging the letters alphabetically: {A, K, N, P, R, U}
Step 1: Words starting with A = 5! = 120
Step 2: Words starting with K = 5! = 120
Step 3: Words starting with N = 5! = 120
Step 4: Words starting with PA = 4! = 24
Step 5: Words starting with PK = 4! = 24
Step 6: Words starting with PN = 4! = 24
Step 7: Words starting with PRKA = 3! = 6
Step 8: PRKAN is the 439th word
Step 9: PRKAUN is the 440th word
The number of 6-letter words, with or without meaning, that can be formed using the letters of the word MATHS such that any letter that appears in the word must appear at least twice, is $ 4 \_\_\_\_\_$.
Let \( f : \mathbb{R} \to \mathbb{R} \) be a twice differentiable function such that \[ (\sin x \cos y)(f(2x + 2y) - f(2x - 2y)) = (\cos x \sin y)(f(2x + 2y) + f(2x - 2y)), \] for all \( x, y \in \mathbb{R}. \)
If \( f'(0) = \frac{1}{2} \), then the value of \( 24f''\left( \frac{5\pi}{3} \right) \) is: