Solve the Problem $y = \sin 2 \pi l t + \sin 2 \pi h t$

Multiple Choice

Solve the problem.
-The sound produced by touching each button on a touch-tone phone is described by $y = \sin 2 \pi l t + \sin 2 \pi h t$
where $l$ and $h$ are the low and high frequencies (cycles per second) in the figure shown.


Touch-Tone phone
Describe the sound emitted by touching the 0 key as a product of sines and cosines.

A) $\mathrm { y } = 2 \sin ( 2277 \pi \mathrm { t } ) \cos ( 395 \pi \mathrm { t } )$
B) $\mathrm { y } = 2 \sin ( 2418 \pi \mathrm { t } ) \cos ( 536 \pi \mathrm { t } )$
C) $\mathrm { y } = 2 \sin ( 395 \pi \mathrm { t } ) \cos ( 2277 \pi \mathrm { t } )$
D) $\mathrm { y } = 2 \sin ( 536 \pi \mathrm { t } ) \cos ( 2418 \pi \mathrm { t } )$