Two point charges are located on the y axis as follows: charge q1 = -1.20 {rm nC} at y1 = -0.700 {rm m}, and charge q2 = 4.10 {rm nC} at the origin (y = 0). What is the magnitude of the net force exerted by these two charges on a third charge q3 = 7.00 {rm nC} located at y3 = 0.400 {rm m}?