An ideal gas is made go to through a cyclic thermodynamics process in four steps. The `Q_(2)= 300J, Q_(3)= - 400J, Q_(4)= -100J` respectively. The corresponding works involved are `W_(1)= 300J, W_(2)= -100J, W_(3)= 100J and W_(4)`. What is the value of `W_(4)`?