A two-stage missile is fired vertically from rest with acceleration as shown in the graph. In 15 sec, the first stage, A, burns out and the second stage, B, ignites. How fast is the missile moving and how far has it gone at t = 20 sec.
A) v = 360 m/s; s = 3.60 km
B) v = 430 m/s; s = 4.30 km
C) v = 500 m/s; s = 5.00 km
D) v = 395 m/s; s = 3.69 km