Complete and use a two-way probability table

A set of catalogue labels is classified by two binary properties

Event A means an item has a marked corner; event B means an item is on the round shelf. The sample space is S, and the complements are A′ and B′

Event A is shown in the rows and event B is shown in the columns. Not A and Not B denote the complementary categories. The entries are counts of items

One item is selected uniformly at random from these recorded items