NASA Trains Astronauts in "Zero-G" by Flying a C-9 Jet $\times$

Multiple Choice

NASA trains astronauts in "zero-g" by flying a C-9 jet plane in a parabolic path,the so called "Weightless Wonder" or the "Vomit Comet" flights.One path the plane takes is expressed as y = y_o + 0.8 x - 2.18 $\times$ 10^-4 x² where y_o is the highest point,and x and y are the horizontal and vertical coordinates (in m) .What is the horizontal speed of the plane?

A) 50 m/s
B) 100 m/s
C) 150 m/s
D) 200 m/s
E) 250 m/s