Can someone give me the MMR range for each division/tier

I'm curve b4. I keep going on winstreaks then occasionally losing. I feel like I shouldn't be in low bronze at this point. I should be b2 at least(MMR isn't high enough definitely). My last loss was my 1st b4 promo game then I won and got promoted due to failing them before then I reclimbed and won. I'm 4 in a row.my MMR is around 980. How much is 1 win? Is it a diminishing return deal while getting consistent wins like now? What are the MMR ranges for each division currently? The articles up now may be outdated.