Solve the Problem $\mathrm { s } = \mathrm { t } ^ { 2 } - 8 \mathrm { t }$

Solve the problem. Give the answer to the nearest tenth.
-The position of an object moving in a straight line is given by $\mathrm { s } = \mathrm { t } ^ { 2 } - 8 \mathrm { t }$ , where $\mathrm { s }$ is in feet and $\mathrm { t }$ is the time in seconds the object has been in motion. How long (to the nearest tenth) will it take the object to move 19 feet?

A) $20.0 \mathrm { sec }$
B) $9.9 \mathrm { sec }$
C) $9.7 \mathrm { sec }$
D) $20.9 \mathrm { sec }$