[" 11.Three charges are placed at the vertices of an equilateral triangle of side ' "a" ' as shown in "],[" the following figure.The force experienced by the charge placed at the vertex A in a "],[" direction normal to "BC" is "],[[" (a) "()^(2)-(4 pi varepsilon_(1),^(2))," (b) "-0^(2)/(4 pi varepsilon_(0)u^(2))," A "],[" (c) Zero "," (d) "Q^(2)/(2 pi varepsilon_(0),a^(2)),]]