`( hati xx hatj ). hatk +( hatj + hatk ).hatj `

What is hati . ( hatj xx hatk) ?

A unit vector coplanar with hati + hatj + 2 hatk and hati + 2 hatj + hatk, and perpendicular to hati + hatj + hatk is : a) ((hatj - hatk )/( sqrt2)) b) ((hati + hatj+ hatk )/( sqrt3)) c) ((hati + hatj + 2 hatk )/( sqrt6)) d) ((hati + 2 hatj + hatk )/( sqrt6))

If a = 2 hati + j - 3 hatk , b = hati - 2 hatj + 3hatk , c = - hati + hatj - 4hatk and d = hati + hatj + 2hatk , then (a xx b) xx ( c xx d) =