Air in a pipe, which is open at both ends, is resonating in its first harmonic mode at a frequency of 956 Hz. If the speed of sound in air is 330 ms−1, which of the following will give the length of the pipe, in metres?
(1) 41(956330)
(2) 21(956330)
(3) 2(956330)
(4) 4(956330)