Hi, 1. I have a MBP (early 2011) with 2x4GB memory modules. I was wondering if buying an 8GB RAM, could I use it together with one of the 4GB modules so there'd be 12GB RAM? Will it work? 2. IF the above installation were ok: should the MHz of the 4GB module match the Mhz of the 8GB module? Or it doesn't matter?