7. Three point charges are located at the corners of an equi- lateral triangle as shown in Figure P23.7. Calculate the re- sultant electric force on the 7.00-C charge. k = 8,99 x 10 N.m?/c? 7.00 C 0.50 m 60 2.00 C -4.00 C Figure P23.7 Problems 7 and 18. 15. In Figure P23.15, determine the point (other than infin- ity) at which the electric field is zero. -1.00 m- _ 2.50 C 6.00 C Figure P23.15 k = 8,99 x 10 N.m?/c? %3D