Astrocytes play a critical role in normal function of the mammalian nervous system. Astrocytes regulate synaptic transmission and plasticity, protect neurons against toxic compounds, and support metabolically to ensure their optimal functioning.
5 per 1,000 because you subtract the 10 deaths from 15 and get 5.
13.99 kilometers is the diameter.
Divide the circumference (43.96) by 2(pi), which should give you a radius of 6.99. You should then proceed to multiplying that by 2, since radius is half of the diameter, giving you 13.99.
