There are 5 spaces and 2 slots, so there are 5*5 = 25 different outcomes.
Think of a table that has 5 rows and 5 columns. There would be 25 cells in this table. Each cell is a different outcome.
The probability tree would have 5 branches on the upper level. Then for each upper branch, there are 5 lower sub-branches. Add up all the possible paths and you should find 25 total paths (each path representing a different outcome).
