Mary buys 8 widgets for $40.00. She adds $1.00 in enhancements to each widget and sells them for $9.00 each. What is Mary's estimated gross profit margin? What is her percentage in profit?

Mary's gross revenue is
  8*$9 = $72
Mary's product costs are
  $40 + 8*$1 = $48
Mary's gross profit margin is
  (sales revenue) - (product cost) = (gross margin) = $72 - $48 = $24 Mary's gross margin percentage is
  (gross margin)/(sales revenue) = $24/$72 = 1/3 = 33 1/3%