Acertain weak base has a kb of 8.00 × 10-7. what concentration of this base will produce a ph of 10.00?

Kb =8.0  x  10^-7
Ph =10.00
POH   =14-10.00=4
(OH-)  =  10^POh
(OH-)  is  therefore=10^-4=1  x10^-4
let  the  base  be  represented  by   letter  B
therefore  the   equation  for  reaction  is  therefore=
B  +  H2O  >HB+   +   OH-
Kb=( HB+) (OH)/b
8.0  x 10^-7 = { (  1  x10^-4)(1 x10^-4)}/  b
8.0 x10^-7= 1  x10^-8 /b
multiply  both  side  by  b
=8.0 x  10^-7b =1  x 10^-8
divide  both  side  by    8.0  x  10^7
concentration  of  b  is  therefore=0.01225M

Sorry i think the answer is b