oh, sorry, when I read "performs 2^n" I interpreted it as "performs 2^n cycles", then I just ignored the rest of your reply, my fault.

I may have reached my answer differently, but never once did superbonzo say I was getting closer or that I had the right idea.
keep in mind that many people come here asking to solve often basic excercises, for which giving even basic suggestions tantamounts solving them. I just saw no other way to help you understanding the solution by yourself but to suggest counting the cycles.