A speaker plays a pure single-frequency tone into the apparatus shown below. The sound takes two paths to an opening where a receiver is positioned. One path is fixed in length, while the other can be adjusted. Suppose that the receiver detects constructive interference at a particular instant. The speaker is producing sound with a frequency of 874 Hz, and that sound travels through the tubes at 343 m/s. By what minimum amount (in cm) should the adjustable path length be increased for the receiver to detect destructive interference?