The domains in a temporary magnet easily lose alignment, but the domains in a permanent magnet keep their alignment.
The temperature inside the copper rod varies linearly with the distance from the hot end of the rod. This means that we can find the temperature at 23 cm (let's call it 'point A') from the cool end by solving a linear proportion.
The temperature difference between the two ends of the rod is

and this corresponds to a length of 81 cm. Therefore, we can write:

from which we find

This is not the final answer actually; this is the temperature difference between the cool end and point A. So, the temperature at point A is
Wavelength - the distance from one wave crest or trough to another wave crest or trough. Amplitude - the distance from the median point or "middle" of the wave straight up to a crest (a maximum) or straight down to a trough (or minimum), which is the peak amplitude; or the distance from a trough straight up to a crest, or a crest straight down to a trough, called peak-to-peak amplitude.