Q: Cannot download El Capitan on this computer - 13-inch, Early 2008 MacBook 4,1 running Lion

My daughter has an older MacBook (early 2008) running Lion. It is equipped with only 2GB RAM and its running OX Lion 10.7.5. I wanted to see if we could upgrade to El Capitan at the Apps Store, but I get the error message "This version of OS X 10.11 cannot be installed on this computer". There's a button on the window that says "Learn More" but it does nothing when pushed. I've seen posts from folks with similar problems, but with different builds and older machines. Any thoughts are much appreciated.