What is the equation for calculating the electrical force, Fe, between two charges?

Fe = kStartfraction q Subscript 1 baseline times q Subscript 2 baseline over d Endfraction.
Fe = Startfraction q Subscript 1 baseline times q Subscript 2 baseline over d Superscript 2 baseline Endfraction.
Fe = kStartfraction q Subscript 1 baseline times q Subscript 2 baseline over d Superscript 2 baseline Endfraction.
Fe = kStartfraction q Subscript 1 baseline times q Subscript 2 baseline over d Endfraction Superscript 2 baseline.

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".