Find the number of paths from P to Q, where each step is to the right or up.
Answer here: https://www.quora.com/What-is-the-number-of-paths-from-P-to-Q-where-each-step-is-to-the-right-or-up
1. Number of permutations of rruuu \(\dfrac{(2+3)!}{2!3!}=\dfrac{5!}{2!3!} = \mathbf{10}\)
2. Number of permutations of rrrruuu \(\dfrac{(4+3)!}{4!3!}=\dfrac{7!}{4!3!} = \mathbf{35}\)
So in total there are \(10*35=350\) paths