AMC 10 2008b Problem 11

Suppose that $(u_n)$ is a sequence of real numbers satifying $u_{n+2}=2u_{n+1}+u_n$, and that $u_3=9$ and $u_6=128$. What is $u_5$? $\mathrm{(A)}\ 40 \mathrm{(B)}\ 53 \mathrm{(C)}\ 68 \mathrm{(D)}\ 88 \mathrm{(E)}\ 104$