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Let a → = − 5 ˆ i + ˆ j − 3 ˆ k , b → = ˆ i + 2 ˆ j − 4 ˆ k and c → = ((( a → × b → ) × ˆ i ) × ˆ i ) × ˆ i . Then c → . ( − ˆ i + ˆ j + ˆ k ) is equal to :

1. –10
2. –15
3. –12
4. –13

Correct answer: –12

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