Regarding An Excel Conditional Formula

Dear Seniors,
Kindly help me how to write this below mentioned conditonal formula in a excel cell "B9" ?
If B8 is Less Than or equal to "1" Then Output should be "0"
If "1.5,2,25" than output "1"
If "3,3.5," then output "2"
If "4,4.5,5" then output "3"
If "5.5,,6,6.5" then output "4"
If "7,7.5" then out put "5"
if "8,8.5,9" then output "6"
if "9.5,10,10.5" then output "7"
if "11,11.5" then output "8"
if "12,12.5,13" then output "9"
if "13.5,14,14.5" then output "10"
if "15,15.5" then output "11"
if "16,16.5,17" then output "12"
if "17.5,18,18.5" then output "13"
if "19,19.5" then output "14"
if above or equal to 20 then output "15"
So is this possible to write so long formula in a cell ?
If yes please kindly help me.
Thanking You In Advance.

Dear Seniors,
Please kindly help me in this regard. Its very urgent for me.
Hope Its not big task for this cite members. Just U have to spend a few minute for this.
Waiting for ur kind reply.

Hi
you are not given properly, so attached your excel file so that I can modify it.