Please explain

Platypuses can sense electric fields as small as 0.002 N/C to help forage for prey. To get a sense of how sensitive this is, how far from a +-46 nC point charge will a field have this magnitude? (Let Coulomb's constant be k = 9 x 109 N * m2 + C-2) Answer in units of m. 002 2.0 points The diagram shows an isolated, positive charge Q, where point B is twice as far away from Q as point A. +Q B O- 0 10 cm 20 cm What is the ratio of the electric field strength at point A to the electric field strength at point B? 1. 2. E E 3. E 4 B