Find the coordinates of the vertices of the figure formed by each system of inequalities.
y + x>-5
y>X-9
3y +x< 13
a. (2,9), (-14, 1), (10,-7)
b. (2,-7), (10, 1), (-14,9)
c. (2,7), (10, 1), (14,9)
d. (2,-7), (-20, 11), (-14,9)