Tier 1 dependent visa timeline after request of extra doc

Hello,
I applied for dependent visa for my UK born baby in 1st week of March and I know its in process currently as a case worker called me to submit an extra document on 31st May, who also said that she will give me her direct postal address in an email, but failed to do so. I posted it the very next day to an address obtained from the customer care center instead.

Can anyone tell me, how long home office may take to process my child's application in this case? Its already been 6 weeks that the biometrics were given.

Thank you