I've been working away on the sample tests but here's one question I just can't get. I'm pretty bad with inverse functions.

Firstly, let's call int(0,inf)[f] the integral from 0 to infinity of a function f.

Let f be a continuous, strictly decreasing, real-valued function such that int(0,inf)[f] is finite and f(0)=1. In terms of f^-1 (the inverse fucntion of f), int(0,inf)[f] is

(A) less than int(1,inf)[f^-1]

(B) greater than int(0,1)[f^-1]

(C) equal to int(1,inf)[f^-1]

(D) ANS equal to int(0,1)[f^-1]

(E) equal to int(0,inf)[f^-1]

Thanks in advance,

David