Explanation:
The Coulomb's law states that the magnitude of each of the electric forces between two point-at-rest charges is directly proportional to the product of the magnitude of both charges and inversely proportional to the square of the distance that separates them:
[tex]F=\frac{kq_1q_2}{d^2}[/tex]
In this case we have an electron (-e) and a proton (e), so:
[tex]F=-\frac{ke^2}{d^2}\\F=-\frac{8.99*10^9\frac{N\cdot m^2}{s^2}(1.6*10^{-19}C)^2}{(933*10^{-9}m)^2}\\F=-2.64*10^{-16}N[/tex]
In this case, the electric force is negative, therefore, the force is repulsive and its magnitude is:
[tex]F=2.64*10^{-16}N[/tex]