If f(b)=b^2 and b is a positive integer, which of the following CANNOT be the value of f(f(b))?  Choose the correct choice from the following answers:
A) 1
B) 81
C) 200
D) 256
E) 625
f(b)=b^2   f(f(b)) = (b^2)^2 = b^4   Therefore f(f(b)) will be numbers that are 4th power of other numbers.   Checking the options:   1 = 1^$   81 = 3^4   200. This cannot be written as the 4th power of any number   256 = 4^4   625 = 5^4   Answer: 200
<result>C</result>
If f(b)=b^2 and b is a positive integer, which of the following CANNOT be the value of f(f(b))?