Solve the all parts of given problem:
Problem: Three equal positive point charges of magnitude Q = 7.00μ C are located at three corners of a square of edge length d = 11.0 cm. A negative charge -21.00μ C is placed on the fourth corner.
Part A: At the position of the negative charge, what is the magnitude of the electric field due to the three positive charges?
Part B: What is the magnitude of the attractive force on the negative charge?
I just want the right answer for above problem, Thanks!