A company produces and sells a product at a price depending on the number of units sold. The price per unit $p$ in dollars is given by the function:

$$ p = -0.5x + 20 $$

where $x$ is the number of units sold. The total revenue $R$ from selling $x$ units is calculated by the formula:

$$ R = p imes x $$

What is the maximum total revenue the company can achieve, as a whole number? Round down if necessary.