Zakaat calculation

1. Do we pay Zakaat on platinum and diamonds and 9 & 18 carat gold? one mufti said yes another said no only for 22 or 24 carat gold???

2. I’m a doctor and have a surgery, my medicines are included in my consultation fee, do i pay Zakaat for my stock of medicine or do i pay Zakaat on whats left in my bank balance once a year or do i pay Zakaat on all income made before expenses?
Please explain how to go about calculate my zakaat?