Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2008/iii/paper-8/5/i/solution

Take , the function Hopf algebra of a finite group. Multiplication is pointwise, and
The group associativity, identity and inverse laws respectively verify coassociativity, the counit and the antipode; pointwise products show that are algebra homomorphisms. Thus is a commutative Hopf algebra.
For and , using right-to-left permutation composition, whereas . The delta function has but . Therefore .

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