I'm not sure how to solve this question, can someone help explain how to do it?

1) Given Charge 1 is -400 JC and is at the origin (0 m, 0 m) Charge 2 is 500 JC and is at point (0 m, 1 m) Charge 3 is 200 UC and is at point (5 m, 4 m) What is the force on Charge 3 in terms of its magnitude (r) and direction (0)