At the end of a certain year, the four organizations ranking 5 through 8 in home Internet users in the United States were eBay, the U.S. Government, Amazon, and Lycos, with a combined audience of 112 million users. Taking x to be the eBay audience in millions, y the U.S. Government audience in millions, z the Amazon audience in millions, and u the Lycos audience in millions, it was observed that
y − z = z − u
x − y = 3(y − u) + 7
and x − y + z − u = 28.
How large was the audience of each of the four organizations at the end of that year?