If

→

a

=

^

i

+2

^

j

+3

^

k

and

→

b

=2

^

i

+4

^

j

−5

^

k

represent two adjacent sides of a parallelogram, find unit vectors parallel to the diagonals of the parallelogram.
OR
Using vectors, find the area of the triangle ABC with vertices A(1,2,3), B(2,−1,4) and C(4,5,−1).