Three point charges are arranged in a straight line. The point charges are q1 = 10.0 μC, q2 = −30.0 μC, and q3 = 20.0 μC. Charge q1 is 20.0 cm from charge q2, and charge q3 is 30.0 cm from charge q2. Determine the magnitude of the net electric force on charge q1.