who can help me to solve them? Thanks very much~

Question

Hi guys~ I can’t understand this two questions; who can help me to solve them? Thanks very much~

Papermaking
Papermaking is known to have been traced back to China about 105 CE, when Cai Lun, an
official attached to the Imperial court during the Han Dynasty (202 BCE-220 CE), created a
sheet of…
Mechanical Engineering