If A and B are n by n matrices with all entries equal to 1, find $\displaystyle \ (ab)_{ij}$. Summation notation turns the product AB, and the law (AB)C=A(BC), into

$\displaystyle \\ (ab)_{ij}= \displaystyle \sum_{k}\ a_{ik}b_{kj}\ \displaystyle \sum_{j}\left(\sum_{k}\ a_{ik}b_{kj}\right)\ c_{jl}\ =\displaystyle \sum_{k}\ a_{ik}\left(\sum_j\ b_{kj}c_{il}\right) $

Compute both sides if C is also n by n with every $\displaystyle \ c_{jl}=2$

I haven't even done any work on this yet, because first I don't even understand what the question wants, and second I don't even know where to begin.