PHP Query Multiplication help...

$describeQuery = "SELECT (Products.Price * MonthlySales.SalesVolume) as revenue From Products
INNER JOIN MonthlySales
ON
(Products.ID = MonthlySales.ProductCode)
GROUP BY Products.ID";



$results = sqlsrv_query($conn, $describeQuery);

echo '<table border="1" BORDERCOLOR=Black>';
echo '<tr><th bgcolor = "LightBlue">Name</th><th bgcolor = "LightBlue" >ID</th> <th bgcolor = "LightBlue" >Sales</th></th> <th bgcolor = "LightBlue" >Year</th> </tr>';


while($row = sqlsrv_fetch_array($results, SQLSRV_FETCH_ASSOC)) 
  {   
  echo '<tr>';
	echo '<td >' .$row['revenue'].'</td>'; 
	echo '</tr>';
	} 

echo '</table>';


sqlsrv_close($conn);

$describeQuery = "SELECT Name, SUM(Products.Price * MonthlySales.SalesVolume) as revenue From Products
INNER JOIN MonthlySales
ON
(Products.ID = MonthlySales.ProductCode)
GROUP BY Products.ID";

$describeQuery = "SELECT Products.ID, Products.Name, Products.Price * SUM(MonthlySales.SalesVolume) AS revenue FROM Products p

INNER JOIN MonthlySales 
ON
(Products.ID = MonthlySales.ProductCode ) AND MonthlySales.Year = '$desiredYear' 
GROUP BY Products.ID ";