The function $R(x)=-0.5x^2+100x$ gives the predicted revenue $R(x)$, in dollars, from selling $x$ items. If $R(120)$ is approximately equal to $4800$, this means that when $120$ items were sold, the predicted revenue was approximately $4800$ dollars. According to this interpretation, what was the predicted revenue, in dollars, when $120$ items were sold?