A rocket is launched into the air. A few moments after liftoff, the rocket is 40 $\mathrm{m}$ above the ground. After another 5 $\mathrm{s}$ , the rocket is now 200 $\mathrm{m}$ off the ground. What is the average velocity of the rocket during the 5 s part of the flight?
(A) 16 $\mathrm{m} / \mathrm{s}$
(B) 32 $\mathrm{m} / \mathrm{s}$
(C) 48 $\mathrm{m} / \mathrm{s}$
(D) 64 $\mathrm{m} / \mathrm{s}$