$begingroup$ For (a), a simple way to take a look at is that you have lowered your chance Area to just the combinations which have no less than 1 boy: 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 What we do to build the polyphase decimator is design and style the small move FIR filter https://boyspggurugramsector15.blogspot.com/2025/07/find-ideal-boys-pg-in-gurgaon-sector-15.html