Use a calculator to simplify each of the following numerical expressions. Express your answers to the nearest hundredth.
(a) $\left(2^{-3}+3^{-3}\right)^{-2}$
(b) $\left(4^{-3}-2^{-1}\right)^{-2}$
(c) $\left(5^{-3}-3^{-5}\right)^{-1}$
(d) $\left(6^{-2}+7^{-4}\right)^{-2}$
(e) $\left(7^{-3}-2^{-4}\right)^{-2}$
(f) $\left(3^{-4}+2^{-3}\right)^{-3}$