Answer:
Step-by-step explanation:
30 minutes UoU
Every 10 minutes he finishes 20% of the book case.
so In 10 minutes he will have 50% done, In 20 minutes 60%, in 40 minutes 100%
There are enough information's already given in the question. Based on those information's that answer can be easily deduced.
Radius of the sphere = 8 units
Then
Surface area of the sphere = 4 *pi * r^2
= 4 * pi * (8)^2
= 4 * pi * 64
= 256pi
I hope that this answer has come to your help.