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Let a  = 2 i ˆ + 5 j ˆ – k ˆ , b  = k ˆ 2 j ˆ 2 i ˆ 2   and c  be three vectors such that       , 29 c . a . i ˆ c a i ˆ b a i ˆ c                 then c  .   k ˆ j ˆ i ˆ 2    is equal to :

1. 10
2. 5
3. 15
4. 12

Correct answer: 5

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