Sorry if this is wrong section, I'm not sure where else to post. I am stuck with this problem:

f(x)= m * 2^{kx}

where

f(3)=27

f(4)=36

Question is: What is f(6)?

I can't figure how to solve either k or m; or how to substitute either of them for something useful. According to my textbook the answer is 64, but I have no idea how to get there. Any help is appreciated.