Tom buys a pizza and with that same amount of money he could have bought a drink and a hot dog. The opportunity cost is what the the drink.
the money.
the hotdog.
the drink and the hotdog.

Consider an insulating crystal, made up of layers of atoms. what form would you expect the temperature dependence of the phonon heat capacity to approach at extremely low temperatures if the interlayer coupling is i)very strong (rigid coupling), and ii) very weak. explain.