What are the minimum requirements for CPU and RAM?
You can find the recommended specs in the FAQ on UnrealEngine.com.
What are Unreal Engine 4’s system requirements?
For developing with UE4, we recommend a desktop PC with Windows 7 64-bit or a Mac with Mac OS X 10.9.2 or later, 8 GB RAM and a quad-core Intel or AMD processor, and a DX11 compatible video card. UE4 will run on desktops and laptops below these recommendations, but performance may be limited.
I hope this helps.