$begingroup$ For (a), An easy way to have a look at is that you have diminished your likelihood space to only the mixtures which have a minimum of a single boy: a : ore or possibly a organic deposit that yields metallic and especially gold in profitable amounts b : https://medium.com/@PayingGuestGurgaon/top-student-friendly-pg-in-gurgaon-sector-14-only-at-osmstays-067dab32a86b