At Orange County Choppers, Paul Teutul Junior needs to make a circular metal disk with area

The radius of such a disk is inches.

To keep Paul Senior from blowing a gasket, Paul Junior must deviate from the ideal area of the disk, which is , by less than How close to the ideal radius must the Flowjet (the machine that cuts the disk) be to maintain tranquility at OCC?

Answer = inches.

In terms of the definition of , let be the actual radius of the disk and the actual area of the disk.
What is the formula for the function ?
What is the number ?
What is the number ?
What value of is given?
What is the corresponding value of ?

You can earn partial credit on this problem.