Lol, i thought i needed to provide a general structure. Yeah, i got x = 4 in c too.
I thought there must be Al - F - Al bridges, with Al-F half bonds. But i cant thing on what to do with the terminal Al. I can only imagine a circular (Al-F-)4 structure, with 2 CH3CH2- in each Al. But I`m not sure if entropy would let this happen.