Find the least integer n such that f(x) is $O(x^n)$ for each of the following functions:

(a) $f(x) = 2x^2 + x^{4} \log(x)$

(b) $f(x) = 3x^{7} + (\log x)^4$

(c) $f(x) = \frac {x^4 + x^2 + 1}{x^4 + 1}$

(d) $f(x) = \frac {x^3 + 5\log(x)}{x^4 + 1}$