The flight path of a rocket, launched from the ground, is modeled by y = 0.5(20x – x2), where y is the height of the rocket in feet from the ground and x is the time in seconds after it was launched. Find the vertex of the parabola and explain what it represents in terms of the context.

a. (20, 0); rocket lands at 0 feet after 20 seconds
b. (10, 50); rocket reaches maximum height of 50 feet after 10 seconds
c. (10, 50); rocket reaches maximum height of 10 feet after 50 seconds
d. (20, 0); rocket reaches 20 feet after 0 seconds