Answer:
Thus, the payback time for cavity wall insulation is 7.5 years
That would be a maximum of 4 atoms
Construction, like building a home/building, digging, like in a mine, and opening a soda can, where the part to open is a lever.
Reflecting telescope. Reflecting telescopes tend to have larger objective (due to the use of mirrors, mirrors are a lot cheaper than lenses) and have the ability to collect more light, while refracting telescopes are limited to objective lenses with smaller diameters due to their structural limitations (chromatic abbreviation, for example). Therefore, reflecting telescopes should be better at viewing faint distant stars