[" 4.Four point charges "q_(A)=2 mu C" and "q_(B)=-5 mu C,q_(C)=],[2 mu c" and "q_(D)=-5 mu c" are located at the corners of a "],[" square "ABCD" of side "10cm" .What is the force on a "],[" charge of "2 mu c" placed at the centre of the square? "]