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.