1) First of all, we need to find the distance between the two charges. Their distance on the xy plane is
substituting the coordinates of the two charges, we get
2) Then, we can calculate the electrostatic force between the two charges
and 
, which is given by
where
is the Coulomb's constant.
Substituting numbers, we get
and the negative sign means the force between the two charges is attractive, because the two charges have opposite sign.
substituting the coordinates of the two charges, we get
2) Then, we can calculate the electrostatic force between the two charges
where
Substituting numbers, we get
and the negative sign means the force between the two charges is attractive, because the two charges have opposite sign.