The Function S = F(t) Gives the Position of a Body

Multiple Choice

The function s = f(t) gives the position of a body moving on a coordinate line, with s in meters and t in seconds.
- $$s = 7 t - t ^ { 2 } , 0 \leq t \leq 7$$
Find the body's displacement and average velocity for the given time interval.

A) $- 98 \mathrm {~m} , - 14 \mathrm {~m} / \mathrm { sec }$
B) $98 \mathrm {~m} , - 7 \mathrm {~m} / \mathrm { sec }$
C) $0 \mathrm {~m} , 0 \mathrm {~m} / \mathrm { sec }$
D) $98 \mathrm {~m} , 14 \mathrm {~m} / \mathrm { sec }$