Let M be a sequence of 9 distinct integers sorted in ascending order. How many distinct pairs of sequences, N and O are there such that i) each are sorted in ascending order, ii) N has 5 and O has 4 elements, and iii) the result of merging N and O gives that sequence?
(a) 84
(b) 35
(c) 194
(d) 138
The question was posed to me during an online interview.
My doubt is from Counting in portion Counting of Discrete Mathematics