Three Point Charges Are Placed on The $x$ -Axis, as Follows $+ 2.0 \mu \mathrm { C }$

Three point charges are placed on the $x$ -axis, as follows. A charge of $+ 2.0 \mu \mathrm { C }$ is at the origin, a charge of $- 2.0 \mu \mathrm { C }$ is at $x = 50 \mathrm {~cm}$ , and a charge of $+ 4.0 \mu \mathrm { C }$ is at $x = 100 \mathrm {~cm}$ . What are the magnitude and direction of the electrostatic force on the charge at the origin due to the other two charges? $\left( k = 1 / 4 \pi \varepsilon _ { 0 } = 9.0 \times 10 ^ { 9 } \mathrm {~N} \cdot \mathrm { m } ^ { 2 } / \mathrm { C } ^ { 2 } \right)$