Problem 4: ISBN Codes.Every book has an International Standard Book Number (ISBN) code. This is a 10-digit code indicating the book's publisher and title. The tenth digitis a check digit satisfying(d1,d2,...,d10) · (10,9,...,1) ≡ 0 11,where (d1,d2,...,d10) · (10,9,...,1) = 10d1 9d2 ... 1d10 is called ïnner product notation.̈One problem is that d10 might have to be a 10 to make the inner product zero;in this case, 11 digits would be needed to make this scheme work.Therefore, the character X is us

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