Three particles of equal mass 'm' are situated at the vertices of an equilateral triangle of side `L`. The work done in increasing the side of the triangle to `2L` is

Three particles each of mass m are placed at the three corners of an equilateral triangle of side a. The work done on the system to increase the sides of the triangle to 2a is:

Three particles each of mass m are kept at the vertices of an euilateral triangle of side L . The gravitational field at the centre due to these particle is