@Soumyadeep
Have you done a similar problem like this bro? I haven't done one where we have to consider both of them so my working is just getting too complicated. Do you have an example problem ?
However, since answers aren't matching with what I initially did, its most likely that we have to consider h2co3 as you said.
@Soumyadeep
Send working pls.
@Soumyadeep
Wait is this somewhat like simultaneous solubility?