Your niece is deciding whether or not to open a lemonade stand. She expects to sell 20 cups of lemonade for $1 per cup. She already made a sign that cost her $10 and will have $15 worth of additional costs for cups and lemonade mix if she decides to open the stand. If your niece decides to open the lemonade stand, how much profit will she earn? Should she open the lemonade stand? What kind of cost is the $10 spent on the lemonade stand sign?