Al's big saleDiscrete Mathematics Level 3
Discount Al's Thrift Shop is having a one-day going-out-of-business sale in which everything must go!
Al only has four distinct things left in his shop.
All the years that Al has been in business, he's only ever had four distinct customers, and he does not expect that to change today
At the end of the day, the bank representative will come to foreclose the shop, and he will take whatever is left.
How many ways can Al's things be sold to his customers (or taken by the bank)?