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Let , c and b , a    be three non zero vectors such that c . b   = 0 and ) c b ( a      = 2 c b    . If d be a vector s uch that d b    = b a    , then ) d c ( ) b a (        is equal to

1. 4 1
2. 2 1
3. 4 1 
4. 4 3

Correct answer: 4 1

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