Suppose Kendra Gallegos has appointments with 9 potential customers. Kendra will be ecstatic if all 9 of these potential customers decide to make a purchase from her. Of course, in sales there are no guarantees. How many different sets of customers may place an order with Kendra? (Hint: Each set of customers is a subset of the origina set of 9 customers.) The set has subsets. (Type a whole number.)