Choose the system of equations which matches the following graph:
a) 3x + 2y = 8
6x + 4y = 20
b) 3x - 2y = 8
6x + 4y = 20
c) 3x + 2y = 8
6x - 4y = 20
d) 3x - 2y = 8
6x - 4y = 20
