A doughnut shop has a special on its Mix-n-Match selection, which allows customers to select three doughnuts from the following varieties: Boston creme, peanut butter, glazed, jelly, plain, maple, and apple cider. How many different Mix-n-Match selections are possible?
[Hint: Consider when all three doughnuts are the same, two are the same, and none are the same.)
There are possible selections.
(Type a whole number.)