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(i)
Required number of ways $= {3 \choose 1} \times {8 \choose 4} \times {5 \choose 2} \times {6 \choose 4} = 31500$

(ii)
Number of ways for both brother are in team $= {3 \choose 1} \times {8 \choose 4} \times {4 \choose 1} \times {5 \choose 3} = 8400$
Number of ways for both brother are not in team $= {3 \choose 1} \times {8 \choose 4} \times {4 \choose 2} \times {5 \choose 4} = 6300$
Required number of ways $= 31500 - 8400 - 6300 = 16800$ ways.

(iii)
We consider three cases here.
1. Remaining midfield plays as midfielder
2. particular midfield plays defender
3. particular midfield not playing

Required number of ways $= {3 \choose 1} [{8 \choose 4} \times {3 \choose 1} + {8 \choose 3} \times {3 \choose 2} + {8 \choose 4} \times {3 \choose 2}] {5 \choose 4} = 8820$ ways.