In the following exercises, points $P$ and $Q$ are given. Let $L$ be the line passing through points $P$ and $Q .$
a. Find the vector equation of line $L$
b. Find parametric equations of line $L$
c. Find symmetric equations of line $L$
d. Find parametric equations of the line segment determined by $P$ and $Q$ . $P(4,0,5), Q(2,3,1)$