Please kind sir/lady help me with my home work UvU

Wo audio speakers are placed on a vertical rail. speaker a is placed at head-level while speaker b is place at some variable height, \delta yδy, above speaker a. both speakers receive simultaneous input from a sine-wave generator so the speakers each produce a pure sinusoidal sound wave with a wavelength of 0.531 meters. calculate the lowest height that speaker b can be placed above speaker a to produce a minimum of sound heard by person standing \delta x = 7.86δx=7.86 meters directly in front of speaker a.

The ability to make things happen is also called a. heat b. force c. matter d. energy

What characteristics of hv2112 make it the best candidate to be classified as a thorne-zytkow object?