title: javascript to calculate cost then display in html page
body: <p>Just learning javascript and would appreciate assistance to achieve the following:</p>
  
  <p>The visitor can choose options from three drop down boxes (size, color, quantity), then press submit.  Javascript will calculate the value of each and display the result as a value in a div of the HTML page.</p>
  
  <p>EG,</p>
  
  <ul>
  <li>small=$10, medium=$20, large=$30</li>
  <li>black=$3, red=$5, blue=$7</li>
  <li>amount multiplies the above based on qty</li>
  </ul>
  
  <p>How would I achieve this? with the script and change the HTML output result?</p>
  
  <p>Many thanks!</p>