Indigo is planning a party, and she wants to buy some
combination of red velvet cupcakes and salted caramel
cupcakes. She only has $40 to spend on cupcakes. The
red velvet cupcakes cost $2.50 each, and the salted
caramel cupcakes cost $1.50 each. She knows that
salted caramel cupcakes are very popular, so she wants
at least 10 of that type.