$begingroup$ For (a), a straightforward way to take a look at is that you've lessened your probability space to just the combinations that have no less than a person boy: $begingroup$ In figures and psychological investigation, what is denoted by funds $N$ vs lowercase $n$? (the next equality happens since https://girlpgingurgaonsector14.blogspot.com/2025/07/find-ideal-boys-pg-in-gurgaon-sector-15.html