Determine whether the check digit of the ISBN-10 for this textbook (the eighth edition of Discrete Mathematics and Its Applications) was computed correctly by the publisher. The United States Postal Service (USPS) sells money orders identified by an 11-digit number x₁ + x₂ + x₃...... x₁₁ The first ten digits identify the money order; z₁₁ is a check digit that satisfies x₁ + x₂ + x₃...... x₁₀ mod 9