As Shown in the Figure, Three Charges Are at Corners $Q = - 90 \mathrm { nC }$

As shown in the figure, three charges are at corners of a rectangle. The charge in the bottom right corner is $Q = - 90 \mathrm { nC }$ , and all the other quantities are accurate to two significant figures. What is the magnitude of the net electrical force on $Q$ due to the other two charges? $\left( k = 1 / 4 \pi \varepsilon _ { 0 } = 9.0 \times 10 ^ { 9 } \right.$ $\mathrm { N } \cdot \mathrm { m } ^ { 2 } / \mathrm { C } ^ { 2 }$ )

A) $7.1 \times 10 ^ { - 2 } \mathrm {~N}$
B) $5.3 \times 10 ^ { - 2 } \mathrm {~N}$
C) $2.8 \times 10 ^ { - 2 } \mathrm {~N}$
D) $3.8 \times 10 ^ { - 2 } \mathrm {~N}$