Three Point Charges of Magnitudes + 4

Three point charges of magnitudes + 4.0 μC, - 5.0 μC, and - 9.0 μC are placed on the x-axis at x = 0 cm, x = 40 cm, and x = 120 cm, respectively. What is the force on the - 9.0 μC charge due to the other two charges?

A) -0.55 N
B) 0.55 N
C) 0.64 N
D) 0.41 N
E) - 0.41 N