A parallelepiped is shown to the right.

$[4$ marks$]$

Let vec$(x)=$vec$(OA),$vec$(y)=$vec$(OB)$ and vec$(z)=$vec$(OC).$

Express each of the following in terms of vec$(x)vec(y)$ and vec$(z).$

a$)$ vec$(DB)$

b$)$ vec$(DO)$

c$)$ vec$(EA)$

d$)$ Area of parallelogram OCEB