The correct answer is B: 453600.

Key Points:

• The word 'REGRESSION' has 10 letters: R, E, G, R, E, S, S, I, O, N.
• Repeated letters: R appears 2 times, E appears 2 times, S appears 2 times.
• Formula for permutations with repeated letters: n! / (p1! × p2! × ... × pk!)
• Total Permutations = 10! / (2! × 2! × 2!) = 3,628,800 / 8 = 453,600.

Additional Information:

• Factorials: n! is the product of all positive integers ≤ n. e.g., 5! = 120, 3! = 6.
• When a set contains repeated items, divide the total factorial by the factorials of each repeated item's frequency.
• Applications: Counting problems, probability theory, combinatorics.