E5 572G 56RP RAM UPGRADE

Hi,

I want to upgrade the ram on my E5 572G 56RP which comes preinstalled with 4gbx1 kingston ram module.

1. The specs on Acer website shows it has 2 memory slots while CPU-Z and Speccy shows it has 4.

2. What frequency ram should I buy to match the one already installed? In CPU-Z and Speccy, the max frequency is shown as 800MHz with NB frequency at 3092MHz. And the channel is shown as single.

3. If it has 4 slots, what are the ways of upgrading? Do I have to install 4x 4gb or can I do it like 4gb in one slot and 8gb in another? And what are the options if it has 2 slots?

Thanks.