The Chromebook C720 2800 with 4GB of RAM is not available in any store, online or otherise, so I attempted to purchase it from ACER direct online. When I tried to do that from the ACER site I got an error message. So I sent an email to ACER customer support enquiring about the status of the C720 2800 model. This is their reply:
"Hello, Thank you for taking the time to contact us. Unfortunately, we no longer have this unit in stock and we are not going to be able to get them back in stock. However, there should be a new Chromebook model released soon. Please continue to check our site for this information to be added. If you have further questions, please call us at 800.910.2237, or respond to this email. Thank you, eCommerce 800.910.2237"
In other words ACER has discontinued the 4GB model only 3 months after it was introduced! You can either purchase the 2GB model or pay extra and get the newer one that is coming out with a touch screen.