A spaceship of mass 2.30×106kg is cruising at a speed of 4.30×106m/s when the antimatter reactor fails, blowing the ship into three pieces. One section, having a mass of 5.20×105kg , is blown straight backward with a speed of 2.50×106m/s . A second piece, with mass 7.90×105kg , continues forward at 1.30×106m/s.
What is the speed of the third piece?