Answer:
a. If c = 20 cm, then the mass of the brain is m = 5 g.
b. At c = 20 cm, the brain's mass is increasing at a rate of 15.75 g/cm.
Explanation:
From the equation

we have
a. for c = 20 cm

then the mass is m(20) = 5 g.
b. In order to find the rate of change, first we derivate

Evaluated at c = 20 cm, we have

So, at c = 20 cm, the mass of the brain is increasing at a rate of 15.75 g/cm.
Eras and then smaller periods based on geologic and biologic events that occurred during those times. According to geological time scale, there are six eras from the beginning some periods of few eras & then period is classified into smaller units called "epoch"
In short, Your Answer would be Option B
Hope this helps!
Just treat the bead as a point charge.
E = kq/r^2, and E points away from the center of the sphere since the charge is positive.