The NES uses a custom-made Picture Processing Unit (PPU) developed by Ricoh. All variations of the PPU feature 2 kB of video RAM, 256 bytes of on-die "object attribute memory" (OAM) to store the positions, colors, and tile indices of up to 64 sprites on the screen, and 28 bytes of on-die palette RAM to allow selection of background and sprite colors. The console's 2 kB of onboard RAM may be used for tile maps and attributes on the NES board and 8 kB of tile pattern ROM or RAM may be included on a cartridge. The system has an available color palette of 48 colors and 6 grays. Up to 25 simultaneous colors may be used without writing new values mid-frame: a background color, four sets of three tile colors and four sets of three sprite colors. The NES palette is based on NTSC rather than RGB values. A total of 64 sprites may be displayed onscreen at a given time without reloading sprites mid-screen. The standard display resolution of the NES is 256 horizontal pixels by 240 vertical pixels.
 How many mb of Video RAM did the PPU have? (If the question is unanswerable, say "unanswerable")
unanswerable