A point-charge, g, is located at the origin and has a value of -7.9×10-9 C. Point a is situated on the x-axis at x = 0.9 m. What is the magnitude of the electric field at point a?
a) 87.8 N/C
b) 105.4 N/C
c) 123.0 N/C
d) 140.6 N/C