Q$4.$ Consider the bitemporal Dept$($Dno$,$ MGRSSN$,$ VST$,$ VET, TST$,$ TET$)$ schema.

$($a$)$ Give the tuple to record the fact that $$Dept $5$ has employee $123456789$ as manager$$ is valid

starting from $2011-06-15,$ and the fact was added to the database on $2011-06-08.$

$($b$)$ Show what happens to the database when the fact that $$Dept $5$ has employee $987654321$ as

manager$$ is valid starting from $2012-06-01,$ and the fact was added to the database on $2012-05-$

$20.$ Assume the action in $($a$)$ was recorded.