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Let vec(a) = hat(i) - 2hat(j) +3hat(k) ...

Let `vec(a) = hat(i) - 2hat(j) +3hat(k) .` If `vec(b)` is a vector such that `vec(a) . vec(b) = | vec(b)|^(2) and |vec(a) - vec(b)| and | vec(a) - vec(b)| = sqrt(7) ` , then `|vec(b)|` = ______

A

7

B

14

C

`sqrt(7)`

D

`21`

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The correct Answer is:
C
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