The correct answer is (a) 16000 J
To explain: The work done on a body is obtained by calculating the dot product of the force and displacement vector. From Newton’s second law, we get the acceleration equal to 8 m/s^2. From the second equation of motion the displacement covered can be obtained which is equal to 400 m. On taking the dot product of the force and displacement, we get work done equaling to 16000 J.