It is very difficult to suggest any compatible cpu for your oem board.
Based on ark website, the cpu P8400 is compatible with these chipsets, so i would assume that your board will have one of these chipsets.
As a reference, you can check the compatible cpus for these chipsets, and then you will need to check with the board manufacturer whether they have validated the cpu and if there s any bios that is required/
All the best,
Keep in mind that the compatiblity between the processor and the motherboard is determined by the motherboard manufacturer, not by the chipset manufacturer, so I would strongly recommend contacting the motherboard manufacturer, or in this case the laptop manufacturer, for them to provide you a list of supported processors for your laptop system.