Four equal positive electrical charges of 1 μC are held on the corners of a square that is 2 m on a side. What is the magnitude of the electric field at the center of the square?
a. 0
b. 4 × 10⁻⁶ N/C
c. 4.5 × 10³ N/C
d. 9 × 10³ N/C
e. 1.8 × 10⁴ N/C