Solve the Problem $\mathrm { P } _ { 1 } = 0.005 \sin ( 14 \pi \mathrm { t } )$

Solve the problem.
-Two low-frequency sound waves with similar frequencies, producing the pressures $\mathrm { P } _ { 1 } = 0.005 \sin ( 14 \pi \mathrm { t } )$ and $\mathrm { P } _ { 2 } = 0.002 \sin ( 22 \pi \mathrm { t } )$ , combine to form a pressure $\mathrm { P } = \mathrm { P } _ { 1 } + \mathrm { P } _ { 2 }$ . The variable $\mathrm { t }$ is time measured in seconds. Graph $P$ in $[ 0,1.2 , .05 ]$ by $[ - 0.01,0.01,0.001 ]$ and use the graph to determine the frequency of the displayed beats.

A) 8 beats per second
B) 11 beats per second
C) 7 beats per second
D) 4 beats per second