Book Maths Puzzle

In how many ways can 9 different colour balls be arranged in a row so that black, white, red and green balls are never together?

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Book Other Question

In how many ways can 11 persons be arranged in a row such that 3 particular persons should always be together? A company has 11 software engineers and 7 civil engineers. In how many ways can they be seated in a row so that no two of the civil engineers will sit together?