Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2019/iii/paper-138/5/c/i/solution

Only the classes are 2-regular. The trivial module and the natural three-dimensional module are simple; the dual natural module gives the conjugate three-dimensional character. Restricting the ordinary characters to the odd-order classes and using produces the fourth simple character of degree eight. The Brauer character table is
The ordinary degree-eight character restricts exactly to . Since its degree contains the full 2-part of , this simple module is projective and its singleton block has defect zero. Thus

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