Certain birds produce vocalizations consisting of two distinct frequencies that are not harmonically related that is, the two frequencies are not harmonics of a common fundamental frequency. These two frequencies must be produced by two different vibrating structures in the bird's vocal tract. 

a. Wood ducks have been observed to make a call with approximately equal intensities at 850 Hz and 1200 Hz. The mem- branes that produce the vocalizations do not seem to vibrate at frequencies less than 500 Hz. Given this limitation, could these two frequencies be higher harmonics of a lower- frequency fundamental? 

b. If we model the duck's vocal tract as an open-closed tube, what length has a fundamental frequency equal to the lower of the two frequencies in part a?