After Exercising for a Few Minutes, a Person Has a Respiratory

Multiple Choice

After exercising for a few minutes, a person has a respiratory cycle for which the velocity of airflow is approximated by $\pi$ $v = 1.75 \sin \left( \frac { \pi t } { 3 } \right)$ ,

Where t is the time (in seconds) .
(Inhalation occurs when v > 0 and exhalation occurs when v < 0.)

Find the number of cycles per minute.

A) 12 cycles/min
B) 10 cycles/min
C) 15 cycles/min
D) 13 cycles/min
E) 11 cycles/min