I'd go the long way about it to make sure as I'm no good at math. There's probably a shortcut but I have no idea.
One pound = 16 ounces
16 + 12 = 28 ounces total
$2.24 divided by 28 ounces = $0.08 per ounce
$0.08 per ounce x 16 ounces to make up a pound= $1.28 per pound