A rigid tank contains a hot fluid that is cooled while being stirred by a paddle wheel. Initially, the internal energy of the fluid is \(800 \mathrm{~kJ}\). During the cooling process the fluid loses \(500 \mathrm{~kJ}\) of heat and the paddle wheel does \(100 \mathrm{~kJ}\) of work on the fluid. What will be the final internal energy of the fluid?

(a) \(300 \mathrm{~kJ}\)

(b) \(400 \mathrm{~kJ}\)

(c) \(800 \mathrm{~kJ}\)

(d) \(500 \mathrm{~kJ}\).