In Figure water flows steadily from the left pipe section (radius r1 = 2.00R), through the middle

Question:

In Figure water flows steadily from the left pipe section (radius r1 = 2.00R), through the middle section (radius R), and into the right section (radius r3 = 3.00R). The speed of the water in the middle section is 0.500 m/s. What is the net work done on 0.400 m3 of the water as it moves from the left section to the right section?