Your supposed to lay down on the floor but go up to the buildings roof and do it or get out of the building.
I am not sure though...
Answer:
Part a)

Part b)

Explanation:
Part a)
As we know that electric field intensity due to some given charge distribution is given as

now electric flux through a spherical surface of radius r is given as


now by Guass law we know that


now volume charge density is given as


Part b)
Total charge inside the radius R is given as

Answer:
500 hours
Explanation:
The sum of total hours over its lifetime will be given by

Where T is total time, r is rate in decimal and To is the original charge hours. Substituting the original charge hours with 5 hours and rate as 0.99 then the time will be

Therefore, the time is equivalent to 500 hours