9. [15 pts] Consider the line segments connecting points $p_1$ and $p_2$ in each of the following scenarios. Find a vector $\vec{v} = (x, y)$ that represents these line segments.
a. $p_1 = (4, 3)$ and $p_2 = (3, 5)$
b. $p_1 = (-5, 2)$ and $p_2 = (5, 4)$
c. $p_1 = (6, 0)$ and $p_2 = (7, 0)$
d. $p_1 = (4, -1)$ and $p_2 = (-5, -10)$