Find out the amount of the work done to separate the charges at infinite distance .

Explanation

Potential energy of charge system.
`U = (1)/(4 pi in_(0)) [ (q_(A) q_(B))/(AB) + (q_(A) q_(B))/(AC) + (q_(B) q_(C))/(BC)] = (1)/(4 pi in_(0)) [ (q(-4q))/(l) + (q(2q))/(l) + ((-4q) (2q))/(l)]`
`= - (1)/(4 pi in_(0)) * (10 q^(2))/(l)`
`therefore` Work done to separate the charges at infinite distance
` W = U_(oo) + U = + (1)/(4 pi in_(0)) * (10 q^(2))/(l)`