I've done that one and as I pointed out you don't need to check the quantity as if only 1 is bought then you end up adding zero to the price of one, however as the price is always 10 then post 19 is all that is required.
This is really eerie, Brian! I'm used to seeing you help around here, but when I last posted I had seen no posts in this thread from you! And I reviewed all posts just prior to sending my last one!