Graph the Expression on Each Side of the Equals Symbol $\mathrm { P } _ { 1 } = 0.004 \sin ( 14 \pi \mathrm { t } )$

Graph the expression on each side of the equals symbol to determine whether the equation might be an identity.
-Two low-frequency sound waves with similar frequencies, producing the pressures $\mathrm { P } _ { 1 } = 0.004 \sin ( 14 \pi \mathrm { t } )$ and $\mathrm { P } _ { 2 } = 0.003 \sin ( 20 \pi \mathrm { t } )$ , combine to form a pressure $\mathrm { P } = \mathrm { P } _ { 1 } + \mathrm { P } _ { 2 }$ . The variable $\mathrm { t }$ is time measured in seconds. Graph $\mathrm { P }$ 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) 10 beats per second
B) 3 beats per second
C) 7 beats per second
D) 6 beats per second