A Particle (Charge = +40 μC) Is Located on the X

A particle (charge = +40 μC) is located on the x axis at the point x = −20 cm, and a second particle (charge = −50 μC) is placed on the x axis at x = +30 cm. What is the magnitude of the total electrostatic force on a third particle (charge = −4.0 μC) placed at the origin (x = 0) ?

A) 41 N
B) 16 N
C) 56 N
D) 35 N
E) 72 N