A company will need 35,000 in 8 years for a new addition. To meet this goal, the company deposits money in an account today that pays
7% annual interest compounded quarterly. Find the amount that should be invested to total $35,000 in 8 years.

the company should invest $

You can find results and justify them? you can test your hypothesis

Planck decided to assume that atoms could only vibrate at certain frequencies that were whole numbers eg 2f, 3f and so on. others used to think that atoms vibrate continuously

Sounds propagates through some kind of medium. usually it's air, but it goes just as well through solid objects like walls, windows etc. a soundwave will compress the (air)molecules in front of it, and if this increased density wave hits your ears, you register it as sound. solid objects like walls are a lot denser than air, this means that they will damp a wave, but also carry it easier.