手提電腦想加ram,但唔知可以加邊種同點加...

我在用LIFEBOOK S6421 FUJITSU, 以下是電腦的規格,13.3-inch wide LIFEBOOK with Intel® Centrino® Processor Technology and professional mobility at approximately 1.9kg* Genuine Windows® 7 Professional Instant converged communications using built-in 1.3 Mega Pixel camera and dual built-in stereo microphones High brightness SuperFine LCD24 for perfect picture and movie viewing Hot-swappable modular bay device options for ultimate flexiblity Extended battery life for mobile computing with ECO button Health and Environment friendliness with RoHS compliance7 請問可以加那種,及多少的RAM?