For a Person at Rest, the Velocity $\mathcal { V }$

Multiple Choice

For a person at rest, the velocity $\mathcal { V }$ (in liters per second) of airflow during a respira- tory cycle (the time from the beginning of one breath to the beginning of the next) is given by $v = 0.85 \sin \left( \frac { \pi t } { 5 } \right)$ where $t$ is the time (in seconds) .
(Inhalation occurs when $v > 0$ , and exhalation occurs when $v < 0$ .) Find the time for one full respiratory cycle.

A) $5 \mathrm { sec }$
B) $13 \mathrm { sec }$
C) $11 \mathrm { sec }$
D) $12 \mathrm { sec }$
E) $10 \mathrm { sec }$