On page 449, in the solution to problem #5 from chapter 11, the text reads, “… the umber of paths from space to the right of S + the number of paths from space below S.”
The word “umber” should be “number.” The sentence would also probably read better if the word “the” were before each instance of the word “space.”
So, “… the number of paths from the space to the right of S + the number of paths from the space below S.”