Chapter 20.2, Problem 20.2GI

Charge q₁ is located at x = 1 m, y = 0. What should you use for the unit vector $\hat{r}$ in Coulomb’s law if you're calculating the force q₁ exerts on a charge q₂ located (1) at the origin and (2) at the point x = 0,y = 1 m? Explain why you can answer without knowing the sign of either charge.