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(1) "velocity of sound" is the collection of words which is NEVER used in English as a technical term in this context.
The correct term is "speed of sound".
It is because the sound spreads in all directions simultaneously in the media (air; water) - not in one fixed preferred direction.
Speed of sound is the product of the frequency by the wavelength
500*660 = 330000 millimeters per second = 330 meters per second. ANSWER
(b) I can not answer (b), since the post FAILED to provide necessary input data for it.
You use very strange numeration of your questions :
First question is (1), while the second is (b).