B
The formula for circumference is

d, or Pi times diameter
The least it could weigh would be 4 tons by rounding 4.4 down
The most it could weigh would be 8 tons by rounding 7.7 up.
You have to solve for the amount of readers.
=500 readers.
39-(15z+48)/27=35
39-35=(15z+48)/27
4=(15z+48)/27
108=15z+48
108-48=15z
60=15z
z=60/15
z=4