A charge q is at the point x =1 m, y =0 m.Write expressions for the unit vectors you would use in Coulomb’s law if you were finding the force that q exerts on other charges located at
(a) x =1 m, y =1 m;
(b) the origin;  
(c) x =2 m, y =3 m.
You’re not given the sign of q. Why doesn’t this matter?