In the figure what are the (a) magnitude and (b) direction (from x-axis in the counterclockwise direction) of the net electrostatic force on particle 4 due to the other three particles? All four particles are fixed in the xy plane, and q1 = -30.40 × 10-19 C, q2 = +30.40 × 10-19C, q3 = +60.80 × 10-19 C, q4 = +30.40 × 10-19 C, θ1 = 36o, d1 = 3.90 cm, and d2 = d3 = 3.30 cm. 10 19...