Chosen Solution
How much RAM can I put to upgrade my mackbook pro model? by the way the serial number is: W89191G98Q2
*Apple officially supports a maximum of 4 GB of RAM. Originally, this model was only unofficially capable of stably supporting 6 GB of RAM, but as confirmed by site sponsor OWC, it is capable of supporting 8 GB of RAM if updated to Boot ROM Version MBP51.007E.B05 and running MacOS X 10.6 “Snow Leopard” or higher.